So this time I discovered Scapeshift is actually bugged. (I must love that card a lot, huh?)
Basically instead of taking into account only your planeswalker colors it also takes into account the colors of your opponent.
- Against a Bolas this removed everything but loyalty gems from the board. Major boom!
- Then against an Angrath opponent, it left only the blue gems on the board.
Both situations were tested multiple times (as I actually got to cast multiple copies in the same match).
The reason I didn’t notice this earlier was because in AI I kept running into either other G/W planeswalkers or plain white planeswalkers. Hence due to the absolute color overlap it was “fine”.