> Companies of course have the right to manage access to their proprietary source code, for example by only giving access to corporate accounts under their control and reclaiming those accounts when an employee leaves.

This is how it should be done, but is too much overhead for many "IT as a cost centre" companies.

Also, it would ruin my GitHub contributions graph

A simple script and a cron job will fix that problem.

custom fake git history with this: https://github.com/artiebits/fake-git-history