HCU, Navy, N.Tx., Tulsa, Charlotte, Prairie View, La Tech, Memphis, Houston
That's who is in their streak. Of the 9 teams, two are FCS (and not great FCS), and the 7 FBS teams they have beaten had a total of 35 wins among them during the seasons in which they played SMU-- an average of 5 wins/year/team.
The streak goes back to the 2022 season (a season in which BYU defeated them in the New Mexico Bowl). If you exclude 2022 (because how relevant is information from two seasons ago in today's CFB?) during the streak they have played two low level FCS teams and 5 FBS teams at home. The 5 FBS teams they played at home (all last season) had 20 wins among them-- 4/year/team-- playing in the AAC and Conference USA.
I know it sounds weird to us but I think BYU probably would have had a similar (maybe not identical) record to theirs last year playing their schedule-- Defeating Prairie View, Navy, Tulsa, La Tech, N. Texas, Memphis, East Carolina, Temple, Rice, Charlotte, and Tulane, and losing to Oklahoma, TCU, and Boston College.