The small class point is fair enough, but doesn’t explain what people who have been offered are doing, including those who were offered by both.
The explanations that make the most sense to me are a) Utah’s class has yet to commit (which itself cries out for explanation, but it does seem to bear out) and b) the schools aren’t shooting for the same targets anymore.
To me, explanation b), if true, is pretty remarkable. I don’t think Utah is simply going for a class of recruits beyond BYU’s reach (after all, BYU offers are committing to the likes of Ohio State, LSU, and other blue-bloods). The respective recruiting pools are simply, and surprisingly, diverging.