I don’t get this comment. Gnome is not trying to make a walled garden, and Microsoft has taken every chance they get at making walled gardens (Windows phone, windows 8 arm, various proprietary file formats and protocols), they just haven’t been very successful at it.
Python is probably the language that popularized them, if not invented them. They’re saying the team doesn’t like using them.
My take is that other than C++, where it’s reasonable, forbidden language features are a smell for the team not having a healthy understanding of the language