It is true that that is of course faster. However, clang and GCC, both do release memory since with modern C++ software projects, it can take huge amounts of ram to compile them.
https://dmalcolm.fedorapeople.org/gcc/newbies-guide/memory-m...
https://dmalcolm.fedorapeople.org/gcc/newbies-guide/memory-m...
Is it? What do you base that on?
I would guess that this hypothesis was true at one time, but is no longer, due to relative memory latencies increasing that mean that the resulting lack of locality becomes a very big problem.
I think this is empirically support by for example this research result, where epsilon collectors are not the highest throughput.
https://users.cecs.anu.edu.au/~steveb/pubs/papers/lbo-ispass...