The Lone Banana: for Grob's (white's) fortieth, I couldn't understand the waiting move.
40. Rd6 keeps the rook attacking the protected pawn instead of moving to the file that has the unguarded, isolated pawn (e.g. 40. Ra7).
A very brief computer check also disagreed with the text move.
1. Down 3 advanced pawns to 1 pawn on the 3rd rank is a difficult draw against comparably skilled opposition and almost an impossible win.
2. In this case two of the black pawns are well protected and connected.
3. The single white pawn has been separated from the white king and rook and is sure to fall.
4. The black pawn on the first file can still be caught before it queens even with the delay.
5. With white's temporizing on move 40, there is a chance that black will have a pawn on a3 just as black plays Kxc3.
6. Rxa3+ will push the black king back from the third rank, allowing the white king to position in front of the remaining black pawns without immediate fear of a kings-in-opposition-edge-of-the-board style ersatz corridor mate.
7. Maybe white's 40th was not tactically best, but it wasn't significantly worse either.
8. Perhaps it was the shrewdest ploy to increase congestion in front of the advanced, soon-to-become-passed pawns, with the faint hope of forcing a stalemate.