IMO it's the best side of Microsoft. It's something Apple would never do because the result might be too unpredictable and messy.
(Although I’ll grant that WebKit itself is a fork of KHTML from the KDE project).
Where is WebKit source and issue management anyway? It's not on GitHub. I don't imagine Apple providing very well for people, who ask for endless options on a product like VS Code.
I suppose the open source Swift language might be comparable, but I don't think it's anywhere in the same league as VS Code regarding the number of users.