All top schools have extremely high retention rates So transfers would be quite limited at a top school if transfers are only used to replace un-retained students.
But plenty of top schools (other than the HYPS level) take lots of transfers and have those spots baked into their model. At places like UCB, UCLA, USC, UVA, Gtown, BU, ND, Vandy, Cornell, the class size grows larger as the years go by for a variety of reasons.
On-campus housing limits, load balancing, articulation agreements with CCs. Can be good business for the schools, since transfer students can be managed in a way that produces a lot of additional full payors. Also, the transfer students stay “off-the-books” for selectivity and grad rate ranking metrics.