It's a shame they don't have an actual application for a truly offline experience. If they had both, people could have their cake and eat it too.

there are desktop builds https://grid.space/downloads.html that run entirely offline. you can also use the center menu to "install" it as a progressive web app.

It says 'local first' doesn't that mean you can run it locally after downloading? That's how I set up pianojacq, just so there aren't going to be a lot of disappointed people that lose their practice logs if I get hit by bus #9.