They are the only teams who are the sole reason why two other teams are not undefeated. Oregon beat Boise and Ohio St, who each only have 1 loss. Georgia beat Clemson and Texas, who only have 1 loss. BYU beat Kansas State and SMU, who only have 1 loss. Pretty good company.
Cougs still getting some disrespect though in relation to the strength of their résumé. Tennessee for example has no basis to be ranked ahead of BYU.