assuming that what they write makes sense, and i do, theres an OS specific limitation on either Ableton's, or Apple/Microsofts side.
looks like this is the maximum amount of threads running, either 64 real cores or 32 physical and 32 logical.
for that matter 64 cores equals 64 threads.
i don't think this has anything to do with whats available, but what the software is capable of in theory.

hmm, pirates from the future, yeah, or that