So I don't know if this counts as a bug or a feature request, but its simple what I want. Currently, the ONLY way to undo in a custom block is to press the physical undo button. However, in the real editor you can use Ctrl-Z.
What I want to be implemented is, when the block editor is focused, you can press Ctrl-Z to undo. I have, multiple times pressed Ctrl-Z in the block editor, forgetting it doesn't support it. This should be easy to make, and I hope its included in the next update (or the ones following it).