It does not matter. Black is up a pawn and has a passed pawn a7 supported by a rook Ra8. So Be5 to cover the promotion square a1 makes sense indeed. You can even set up a battery Bb2 Qc3 to attack pawn g7. Then you can either invade the 7th rank with Re7 and Rfe1, or pile up Ra1 Ra6 Rfa1 on the a-pawn, all depending on what black does.
g3 is a bad move. When you have a bishop, you want your pawns on squares of the other color.
I am looking to understand what I should have thought in terms of a game plan around move 26. The engine says best move would be Be5, but I really don't understand the idea behind it. Thanks.