You made some wrong assumptions regarding BUSS.
BUSS is more than a replacement of pitch/thrust tables.
BUSS replaces the speed scale and consists of GREEN, AMBER and RED areas based upon AoA and S/F CONFIG, goal is to fly the GREEN.
next to the scale is a pointer which represents the AoA.
The scale range is 10° AoA CLEAN and 20° in any other CONFIG.
BUSS is not inhibited above FL250 but since frozen pitots is only a temporary issue the FL250 restriction is added to the UAS/ADR CHECK procedure.
Initially there was NO FL restriction at all, however switching off 3 ADRs to activate the BUSS comes with increased workload (FMS, Cabin Press and ALTERNATE law).
The law reversion is to ALTERNATE and NOT to DIRECT LAW.
Having it on AF447 may not have made a difference.
You may be right but it could also have made a different outcome.