No one is saying exactly what it stems from - but I think it's pretty obvious
The defense has a ton of swagger about it and plays very physical - the WRs definitely like to challenge them and it boiled over a couple times in OTAs with fights breaking out between the two units
Even after the fights when drills resumed there was some "get back" contact that carried over
The guys were competing, trying to get better and I really have no issue with it .... even when it happened the coaches used it as a teaching moment about staying on the right side of the line
Do doubt the league pulled the tape from that practice and saw some "excessive contact"
As mentioned - it was all fairly publicized and not much of a secret that things flared up a little bit
Personally, I'd rather watch a team keep that attitude and competative streak and lose a couple days of OTAs at the very beginning of June