If you measure the M1 Mac's 1u keys from left edge to left edge, that should still be about 19 mm key pitch.
(But to do it more accurately, do measure multiple keys and divide)
Having the top of the keycap as narrow as 12 mm and not 16 reduces the risk of accidentally pressing multiple keys at once.
But there are still a bunch of keycap profiles that fit Cherry MX that are wider at the top, but the key pitch stays the same. "MDA" might be the most well known.