Open-source software is neither good nor evil. Does microsoft benefit? Yes. Does the community also benefit? Yes
If a developer works for microsoft, then contributes code to Whonix, should that contribution be rejected because its somehow tainted? Of course not, because it benefits the community.
The reasons for keeping it like it is were stated in adding non-free packages by default is it safe?
Has anything changed that would convince Whonix developers to reconsider?
My point is just having non-free packages in itself does not make Whonix a non-secure distribution.
I would agree libre/free is safer and Whonix should use open-source if practical. Although just because its non-free doesn’t mean its back-doored.
There are reasons why VirtualBox has non-free. All of them legitimate. I don’t see that changing unless a reasonable alternative is found.