at least, not completely. It's an unholy combination, to a greater or lesser extent, of a few different methodologies.
1. How they legit think it'd play out on the field: i.e. the result of the thought experiment of every team playing every other team 10 times, and listing by most wins (which accounts for cases like: 6 might beat 5 head to head the majority of the time just due to personnel and scheme matchups, but 6 would drop more games to 7, 8, and 9 than 5 would)
2. Who is most "deserving." An undefeated MAC team is ranked in the teens because they did all they could do, but everybody knows the top third of any power conference would beat them head-to-head the majority of the time, and it does often play out that they get shellacked by some 5th place ACC team in a pre-Christmas bowl game
3. The self-fulfilling prophecy method of assigning the number to a team that you think the rest of the pollsters will assign them when the season is over and the dust settles, i.e. the pollster wants to be proven "right"
The problem is, any one pollster can hide behind any one of these to install whatever bias he/she has. And that ambiguity is used to great effect to keep the power in the teams that have the power. They're the ones that get the benefit of the doubt because they've always gotten the benefit of the doubt, but to be fair, that's because they've historically backed it up.
Should BYU be ranked ahead of any/all of the 6 teams ahead of them with a loss? Strictly under the "deserving" section, you bet. But under the thought experiment one, if BYU played each team in the top 25 ten times, would they come in more than 11th or 12th in win total? Eeeeemaybe?
But that's the reason a committee would exclude even a 12-1 BYU team coming off a close loss to an undefeated Iowa State team in favor of a 10-2 Alabama or LSU who didn't even play in their conference championship.
So, while it's great that there's no question, if BYU wins 16 straight, they're National Champion, and in that way their destiny is finally in their own hands, but the reality is that a loss or two come to most of even the best teams, and the biases of the pollsters or committee control a significant amount of "at-large" destiny. And that still sucks.