Oops, I messed one thing up in that speech in the stream.
The weird narrower "walls" are actually in Japan Set 1.
Set 3 is the oldest, Set 1 in the middle, Set 2 is the most recent. (I don't know why MAME numbered them this way, usually they go in reverse-chronological order). This site shows the chronology:
http://tcrf.net/Donkey_Kong_%28Arcade%29They brought in the pixels in Set 1 in order to keep people from doing the floor jump. Then they fixed the floor, put the walls back where they belonged, and released Set 2. After that came the US sets.
So Japan Set 1 is the oddball. You can try the weird walljumping yourself in MAME.
In chronological order, the ROM sets are:
Japan Set 3
Japan Set 1
Japan Set 2
US Set 2
US Set 1
Nobody knows, or will likely ever know, the revision dates, except for the last revision (US Set 1), which was released in December of 1981, which is also when they started making the two-board sets.