First, if you use the arrow keys to move around, the cursor lags and even disappears. This is really not useful when trying to reach a position in an editor.
Second, emacs split buffers (C-X 3 splits the buffer into 2 side-by-side windows) has a problem. The screen refresh sometimes trashes the display. It can be recovered with C-L, of course, so the data isn't damaged but it is annoying. The cursor control is even worse in this configuration. Sometimes the cursor leaves the current buffer and ends up somewhere else on the screen so it appears you are typing in a random screen location. C-L recovers this and you see the data in the correct place.
Third, rather than using a keyboard macro I used "galloping fingers". That is I repeatedly hit
1 down left... 2 down left... 3 down left, in overwrite mode to create columns of numbers.
I've been doing this for years (I've been programming for 50 years). At this point my fingers are, like a drummer, highly reliable. I get a rhythm going and rarely fail... except that on WSL some of the keystrokes get lost so I end up with missing numbers or in the wrong column. It happens about every 50 or so numbers. I notice that it seems to happen when emacs autosaves. So somehow the autosave interruption is losing keystrokes.
I find it hard to believe that keystrokes get lost but that appears to be at least one of the problems. It seems also to be related to "injected keystrokes" in a keyboard macro. Cursor control is also badly broken. This might be related since cursor movement is keyboard driven.
I don't have Windows source code so I'm only guessing.