Actually, that commit has an independent refleak that was fixed (!) regarding the small integer cache. Seems that the actual commit that made the new leak is:
commit 2582d46fbcf7bdf86b9cf4016850b8d155267ac6
Author: Victor Stinner <vstinner@python.org>
Date: Fri Nov 22 19:24:49 2019 +0100
bpo-38858: new_interpreter() reuses pycore_init_builtins() (GH-17351)
new_interpreter() now calls _PyBuiltin_Init() to create the builtins
module and calls _PyImport_FixupBuiltin(), rather than using
_PyImport_FindBuiltin(tstate, "builtins").
pycore_init_builtins() is now responsible to initialize
intepr->builtins_copy: inline _PyImport_Init() and remove this
function.
Reverting this commit fixes the refleaks in atexit at least