I've noticed that when players come back from a torn ACL, they might be technically ready to play. However, that doesn't mean they are ready to perform at the level they left off at. It comes down to confidence in the results of the surgery, being in training camp condition, and some rustiness.
Even Michael Irvin didn't look right when he came back from his surgery in 1990. He came back after game #6 and averaged two receptions a game for the rest of that season. However, he broke out in 1991 with almost 6 catches a game and made 1st team All Pro.
Gallup probably won't be himself until 2023.
It's a mental thing. Hard to trust your knee when it failed you, and I imagine in the back of their mind they're unsure if it's really back to 100%, or at least close to it.
I had a similar occurance many years ago doing squats, was in the gym with one other person and they manged to talk me into trying to do a fair amount more weight that I had been doing. Well I got out of form and had to just chunk the bar over my head, scared the you know what out of me. Next time I did squats my knees shook and I had to quit for a couple of weeks before I could get back to what I had been doing before.
And that was just a scare, not a major injury.
It has always, until Adrian Peterson came back in 8 months and was just as good as before, widely held that it took a full year to recover from an acl tear. Gallup's not going to be at a year until February.
Cut the guy some slack...
