As mentioned in my post, the same principle applies at less selective privates, as well as less selective publics. For example, you mentioned Georgetown and American. I’d expect Georgetown has a high concentration of excellent students who are doing A-quality work in their classes, so I’d expect to see a higher average GPA at Georgetown. In a report a few years ago, the average GPA among students at Georgetown was in the 3.5 to 3.6 range. A report during the same period mentions the average GPA at American is 3.3. Of course some specific colleges are exceptions, but the point is I wouldn’t assume that choosing a not as selective safety will help you maintain a higher GPA than the more selective reach, as colleges with a smaller portion of stellar students tend to give top grades to a smaller portion of students.
One of my roommates at Stanford was not at the top of his class. He had a below average GPA among Stanford students, and ended up switching to a major that has reputation for being easy at Stanford. However, this below average GPA among Stanford students was an overall GPA in the A- range. One would have to be near the top of their class to get a similar GPA at most flagships. He also went to an excellent law school, and now has a job that he loves at a great firm . Maybe he would have had a higher GPA at Stanford. Maybe he would have had a higher GPA at the flagship. Who knows? One person samples aren’t very meaningful.
Yes, many parents are full pay and have less expensive options at lower sticker price colleges. Similarly, many parents are not full pay and have less expensive options at highly selective colleges with excellent FA. In any case, I didn’t say that they’re were not valid reasons for choosing a less selective college. In fact I said the opposite, listing various reasons why a student might choose both more and less selective colleges.