They took a step towards this with https://docs.python.org/3/library/gc.html#gc.freeze but it doesn't go as far as disabling refcount touching outright. I've experimented with doing that, both per-object and just globally, and the results really were promising if your forkserver can keep up with providing the necessarily much shorter-lived worker processes.
Thanks for this link - I had completely missed it (I think I was just expecting to disable gc entirely or perform some rudimentary surgery on its linked list)