That’s fair. From my experience I probably wouldn’t notice a difference if the thumb keycap would be larger as the point of contact is quite small and not a flat area so the keycap doesn’t have to provide a large area.
For reference my keyb: Piantor, Kailh Choc V1, Red Pro switches (35g) with MBK caps. Actually, I consider going even lighter on the switches (blue/pink: 20g), at least for the pinkes