To expand on this: you may not see any issues at first, but during the period of time where the nix store is mounted read/write, other programs (that are badly written and expect to be able to modify files where their program is installed) can silently edit files in the nix store and cause issues with your system. You also open yourself up for user error, obviously.
This method is like using a hammer to put a screw in your wall - hammers are for nails, not screws, even if the screw happens to go in - and is misinformation. Use the tools for the purpose that they are designed for.
To that end, I don’t use gnome, but someone else seems to have figured this out already: