Yeah, right now, almost all the new “configuration” read by Py_Main() is ignored and will not be applied. Python keeps the “old” configuration read by Py_Initialize().
The problem is that many Python objects are kept alive between Py_Initialize() and Py_Main(). For this reason, it’s not possible to change the memory allocator in such case.
I would suggest to deprecate calling Py_Initialize() before Py_Main().