Illini Ref- if you'll utilize the search function here, you can find several discussion threads about this scenario. As it stands for what appeared to be the majority of officials opinions here, BY THE BOOK, this a legal play as there is no definition of
inbounds. A minority opinion was that it is a foul but I don't think "ULC" (unsportsmanlike?) was rendered as the method of penalizing it.
I understand both POV on this topic and would hope to a) never actually see it on the field and b) hope the Fed cleans this up-which will probably take 3 years of refining a definition as they work through the Law of Unintended Consequences.