I believe you are right, except that the delegates will be divided proportionately, not evenly. So, if the WTA trigger of 50% is not met by any candidate, then any candidates that exceed the 15% threshold will divide the delegates proportionately.
Exception: If two or fewer candidates meet the 15% threshold and the 50% trigger is not met, the threshold I’d dropped, and the division is truly proportional. With only three in the race, that is certain if none gets the 50%
Example: If Trump gets 14%, Kasich gets 38% and Cruz gets 48%, then the delegates would be T 6, K 15, C 19.
Example: If Trump gets 20%, Kasich gets 32% and Cruz gets 48%, then
the delegates would be T 8, K 13, C 19.
So bottom line, Utah really doesn't matter much in the whole scheme of things.