All that's necessary is to be facing left when entering the door. Buffering a left press will get Kuros to the top step on the first jump with wizard 2. You don't need to press jump. This works consistently because of the height of wizard 2's jump. Wizard 1 has a slightly lower height, so the horizontal subpixels do come into play there.

after watching it again yeah, it seems even though I turned to the left on the second attempt I didn't buffer another left press, which I did along with pressing jump on all the other attempts, I thought it was because i didn't buffer a jump that the 2nd time failed, not because i didn't buffer left.

Good to know now :)

Edit- I'm not sure how exactly subpixels work, but in an any% run where you would only have Wizard 1 could walking into the slope potentially give a consistent subpixel?

Unfortunately, I haven't found a way to make the game reset the horizontal subpixel value. It starts off at zero but only ever changes when Kuros moves horizontally. Actions such as entering doors usually change the horizontal position to fixed numbers, but the subpixel value is left alone. Walking into a slope will just add or subtract the appropriate subpixel amount based on how much Kuros moves.