Last I checked "post" meant any deep route slanting towards the middle of the field while "flag" went to the sideline. Of course I'm aware football coaches rename the same stuff every couple of years.
A post can be toward the middle of the field or sideline. I am sure that it can go by the term flag, so I am not going to say you are wrong. The difference between a post and a corner is where the route ends up, because at its base they are the same look on a route tree.
It hasn't changed.
The post route has always been a straight ahead route that then angles toward the goal post ...a skinny post breaks into the angle sooner and tries to get in that soft spot behind the backers and in front of the safeties. Still angling toward the goal post.
The outside is a flag route. Named that because manys moons ago the pilon was a flag.
The flag route technically runs straight then a step or two toward the safety or post then breaks hard for the flag (pilon) direction.
Fly pattern is straight ahead. Go route is same thing.
Stop and go is mimicking a stop and curl route and take off in a go route trying to catch the DB biting on the curl route. Works great on an aggressive DB.
Out and up
The receiver cuts out toward the sideline but then turns up on a go route. Another trying to catch an aggressive secondary player too eager for an interception.
Flare route is a running back arcing from his backfield position to the flat. The flat is a reference to the part of the field that gets flat from a crown in the middle. (For drainage)
It's really around the 5 yard mark down field but nearing the sideline.
Spot pass is the lateral pass (not backward) quickly to the receiver. Usually caught at the line of scrimmage and since it's a pass in and around the LOS or behind, blocking can happen immediately, pre catch. Some of the trendy call it a WR screen.
TE drag is the tight end making a radius on his cut usually right out of his three point stance and dragging parallel to the line of scrimmage. Usually 5-7 yards deep.
An old school way of thought of course was most routes within a play were all decoys except for one.
Example....
The QB is under center with the two backs in the I formation. A WR to the left up on the LOS. He's covering the tackle. A receiver in the slot to left(off the LOS). To the right we have a receiver off the ball as the TE is convering the tight tackle. The ball is snapped and we're selling a B power 44...I right 44...whatever you want to call it. That's the tailback (the #4 back) following the fullback going through the 4 hole. (That's between the guard and tackle.) We're running a play action fake on this. Faking the handoff trying to draw the linebackers up.
The left receiver runs a go route, the right side runs a deep post. The tight end runs a drag route (going from right to left parallel to the LOS 5-7 yards deep. A good tight end will feel his way through the defense and get us as much yardage on this drag as he can thought. It could be much more than 7 yards.
The slot receiver is going to run a "deep in"
about 12 -15 yards downfield.
We have a lot going on in this play but it's all smoke and mirrors. Days...many days ago.... at the amateur level QB's didn't go through multiple reads on a play. They were all decoys but one route. In the above instance everyone is the decoy but the tight end. We're selling the play action to draw the linebackers up, this clears out for the tight end dragging across the field. The receivers are running off the secondary. The slot running the deep IN is trying get the attention of some defender. Hopefully the nichel back or rover follows him.
If all goes as planned this will leave a huge vacated area for the tight end to catch the ball in stride for a good chunk play.
The above type of play and similar ones were run quite a bit back in the day. In college and high school coaches didn't trust QB's and honestly a lot didn't have the ability to look at 1,2,3 receivers or go through a progression.
A lot didn't possess the ability to make all the throws to all the zones on the field.
It was decoys and throw to a specific player.
Don't laugh but there are many times...too many times...I can see Ian Ian Book's actions and he knows before the snap exactly where he's going.
I'm serious and don't laugh but someone is telling him to do exactly that on a lot of plays. Far too many plays. When that play is not open he bails. Another reason he leaves the pocket way too early.
The above is an old school passing play philosophy and believe me when I tell you Book is doing sine very similar things. Ordered to do so I'm sure....but...
What happens on said play when the receiver running a post is ignored because the slot receiver ran a deep in and the safety just bit hard on that route. Well a QB should be able to read this and now his target becomes the deep post as that receiver has now got behind the defense. We must make that throw.
Do see Book taking advantage of those type of situations? Once in a blue moon. Maybe. Mostly its him bailing on the pocket and play and running for 8 yards. Everyone gets all giddy thinking Book is now becoming dual threat but what they didn't see is the gravy train touchdown running a post pattern wide open. Just put the ball up and let him run under it.
The above scenario is missed entirely way too much by the Brian Kelly QB's. These are the adjustments mid play that beat elite teams. These things allow you to keep pace in a shootout against a great team. Scoring quickly and with ease.
We don't possess any of the above.
Business as usual.
Timid and tentative.