I’m sure that’s true that the number of courses varies widely and I do not doubt that larger schools offer more. I don’t know how many math majors plan on continuing math in grad school, I’m guessing that’s a minority, but if that’s the goal it should be taken into consideration.
Williams math majors seem to mostly go right to work but a few are doing “top grad program” PhDs in math or related subjects. https://math.williams.edu/majors/post-graduate-mathematics-major-plans/
I think it’s @circuitrider who has a lists of top feeders to math PhD programs and as I recall LACs are very well represented but I may not remember that correctly.