Clicking around it looks like some of the higher Utah gates are up around 4655, whereas the higher BYU gates are only 4650. So both are reporting the highest elevation any portion of the stadium is built at.
Which is... kind of meaningless. Your values are more accurate for the playing field, which takes about 9 feet off of BYU's but closer to 25 off of Utah's reported elevation, this flipping BYU ahead.
FWIW, Air Force Academy also does this, adding that couple extra feet on