seems as if even the officials don't know what's legal and what's not
Well, it's not just the officials. The League chimed in and fined him too.
I have to tell you, if that play is not legal in the NFL, I have to SERIOUSLY consider bidding adieu to the NFL.
Digger timed that hit to post possession and drove the receiver out of bounds so that he could not get his feet down. He used out of bounds to nullify the play. There was no head to head and it was necessary to break up the play. If the fine stands at this point I'll likely not devote the time and energy to a league that is in complete disarray.
Personally, I think its time for a rival league. A new league that does not allow blatant head to head's on defenseless receivers but provides modern equipment for it's players and negotiates contracts with clear language to participate they assume the risk of concussions which are not clear infractions.
If the fine stands, I'll try to convince as many people as possible to join a "fishing league" as well. Fall fishing is beautiful, fun and the guy that sells you the fishing gear can't take it away from you at his whim.