Microsoft employs many people that are open-source advocates. Someone's perspective on that would not impact their status in an interview.

If anything, the reason feedback took forever to him was because someone may have asked for an exception to the interview failure so they could hire him. Large companies are behemoths and things do go wrong, mistakes are made, and Microsoft did own up to it in this case (https://devblogs.microsoft.com/commandline/winget-install-le...) but open source did not play a part in it.

Source: myself, I worked at Microsoft in a past life and did many interviews. No one cares about someone's stance on open source anymore.