The smaller iPad pro moved away from 4:3 aspect ratio a while ago.
Pretty sure the pixels on those displays are square, so you can calculate the aspect ratio from the resolution.
The 13” is 4:3. The 11” is around 16:11.
The change in aspect ratio was one of the reasons why I switched to 12.9” in 2018 and I never got used to the larger size. Haven’t bought an iPad since then until today, going back to 11”.