Strange question, but here goes....What is the consequence of a bag tagged for gate check not left at the end of the jetway but brought on board instead?

So, here's the background. Earlier this week I was flying back to Philly from MIA via CLT. I decided to go standby on an earlier flight and didn't clear standby until well into Zone 3 boarding. As I was handed my ticket, the GA also tagged my bag for gate check (off topic but in the past when going standby i usually get a valet tag, was this just GA going A&B?). With tagged bag in hand I bypassed the long line at the gate by using the preferred access lane and made my way down to the jetway.

Upon reaching the plane I left my bag at the end of the jet way and started to board when I noticed several overhead bins still empty. I started to get my retrieve my bag when the FA told me I wouldn't be able to carry it on without letting the GA know since it was already scanned. I just said fuhgetaboutit, since by the time I went back there any remaining space would be gone.

As I settled into my seat, I started to second guess my actions. Would carrying my bag on really cause an issue? I can't imagine they would have held the AC if the bag didn't show scanned onto the plane.

In the end I rolled with it since in the big scheme of things I got home early and later found out my original flight was delayed over 3 hours.