NCAA men's arbiter page posted a link to the following story about sideline plays in tight arenas, referencing the Kansas/Oklahoma play:
Policing of out-of-bounds plays by Big 12 referees has been more noticeable | News OK
A few interesting quotes by Curtis Shaw:
"If (the inbounders) don't have room to back up at least three feet, we try to move the defending player back," Shaw said. "Tell them they have to stay back."
"Technically, there's no rule against it as long as they're not stepping on the out-of-bounds line," Shaw said. "If they step on the out-of-bounds line, we'll give 'em a delay-of-game warning the first time.
"But if they're just jumping in the air and they're inbounds, there's not much that can be done."