Technically it depends on the ranking secret ranking formula, where SOS is just one of many mysterious parameters. There is no guarantee that BYU or any team gets in with a 4, 8, 12, or even 100 team tournament. That's because the secret formula is ... well secret. However, if there is any modicum of trust that the secret formula is not completely arbitrary, then having more teams in the tournament increases the probability that any one team gets invited.
But that's the rub ... since the secret formula is totally secret and completely non-verifiable, any trust that the formula is not completely arbitrary is based completely on non-substantiated faith.