Correction: The pycache is in fact redirected to the new '~' folder.

In any case, I tested a bit on Debian Bullseye (Python 3.8.6) and Ubuntu 20.04 (Python 3.8.5) and it seems ~ is not expanded in the environment variable Debian. I'm a little uncertain what is the expected behaviour here, but the sys.pycache_prefix variable returns different results on the two platforms:

With environment variable set to ~/.pycache on 3.8.6 (on debian testing), I get the following:

Python 3.8.6 (default, Sep 25 2020, 09:36:53) 
[GCC 10.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.pycache_prefix
'~/.pycache'
>>> 

Doing the same on 3.8.5 on ubuntu 20.04 produces:

Python 3.8.5 (default, Jul 28 2020, 12:59:40) 
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.pycache_prefix
'/home/******/.pycache'
>>> 

Still, perhaps the pycache_prefix should expand the ~ on linux?