Tactics 20554 (B+pawn vs pawn)

it.lichess.org/training/20554

After ...a2, if Ra6 instead of Rb6, i see ...a1=Q; Rxa1 ...Kxa1. This endgame is, if not draw (are there any tablebaser or strong endgame players?), at least though for black. Or I'm wrong? If I'm right shouldn't the exercise move - Rb6 - be wrong?
R.

It's a fairly simple win then.

Black will win white's f-pawn and queen his own.

I don't even know how White could try to make that complicated.

Black's just going to walk the king over, and the bishop will let black win any tempo he needs to make white's king give ground.

If White tries to play Kd2 after the trades, then the bishop just relocates to the a8-h1 diagonal by Ba4-c6, and then black goes with the same plan: march the king over, and when you need white's king to give up ground, move the bishop.

Cheers!

Thanks! I'm very weak in endgames, so thanks for the articulated answer.

R.