The big deal is that 100K+ users were relying on those properties not being mangled so that they can use an extension that allowed them to customize arbitrary pieces of the UI to make it more ergonomic for their screens (change fonts, change paddings, hide elements). Personally, the default UI wastes too much of my laptop's screen space, so when I want to edit multiple files plus having a browser on the side, it's just impossible without these tweaks, so this is a deal breaker, as I can't update VSCode anymore unless this is addressed somehow.

edit: And it's strikes me as odd that you'd want to basically screw over all the demographic of what is your "power users", meaning those that have the ability and the desire to tweak things.