Drill: Endgame Fundamentals - Bishop, Pawn vs Knight

Hello chess lovers (especially those with more endgame knowledge than myself!)

I've been going through the Drill section of chess.com and came across the endgame drill mentioned in the title. I can't seem to figure it out. I'm not saying the engine is wrong, but I can't make sense of why some moves work and some don't, and not consistently. There are also seems to be a strange pattern where every move I make is described as the best move by the engine, which seems highly unlikely.

At any rate, the move which works most commonly is 1. Bg7, where Black captures the Bishop with the Knight, and the Pawn is allowed to Queen. But... Black is not forced to capture the Bishop as far as I can tell! I've tried it many times and sometimes the engine captures, and sometimes it does not. When it doesn't capture, the King moves instead, and 1. Bg7 is still described as the best move.

I can't figure out where to go from there. As far as I can tell, the King can't be forced off of the triangle of b6, b5 and c5, since b5 is a white square, and if ever the black King is on b5, and the white Bishop plays a "waiting move", staying on the a7-g1 diagonal, Black then has the opportunity to play Nf6+ and it's all lost.

Any help? Are ideas way off? What is the winning strategy?

banana