I have never heard about such a restriction for plugins.
And on the plugin page for Grammarly, it says it gets "Access your data for all websites":
You've never seen the popups? If a WebExtension doesn't request access to all sites, it can only access sites that it's activated on by pressing the toolbar button (MDN refers to them as action buttons if you want to take a look). The problem is that most extensions that aren't site-specific are useful because they have access to all sites, but that doesn't mean that's a requirement of the system.
Ok. Then it's probably that every time I looked at an extension it wanted access to any site.
Re:Mastodon – Simplified Federation
by The_SamminAter on Saturday November 05, 2022 @10:27AM
(#33481785)
Heads up about Grammarly: https://news.ycombinator.com/item?id=30470457
You can turn it off for specific sites (via Grammarly settings) OR you can turn it on only for specific sites (via browser settings). The process is different depending on whether you are using a browser extension or desktop integration. Here is an example for the browser extension: https://support.grammarly.com/hc/en-us/articles/115000091612...
It’s how I run grammerly, which is a descent enough grammar checker except I never want it to correct my chat posts, or GitHub comments.