This is an interesting theory, but practically speaking, thinking of wealth vs. Harvard lineage has little to do with the social trend numbers you present.
The “wealthy donor” advantage only becomes manifest when the development office has placed a candidate on its ranked list of applicants that it provides for suggested incorporation into the Dean’s Interest list. The overlap of this list with the Harvard lineage candidate pool waxes and wanes. The overlap is small enough that it isn’t really predictable from larger trends that you quantify. If you are wealthy, and your child is not on this list, your “SES” means no more than all the soft advantages that people of means have…but, you also do not have the admissions advantage that being from a disadvantaged background (eg, first generation) tangibly gives.
The engagement Harvard seeks to cultivate from its alumni is not about only about money, but a desire to have an energized and loyal constituency that helps to keep the Harvard “brand” strong and desired by a broad aspirational population.