I think proton has two levels of 'killswitch' on it's VPN. The regular one is more of a 'killswitch but only when you have the app open' while the extra options are supposed to make it an actual kill switch. Whether or not this second level is completely effective I can't say.
Binding your client to the vpn interface is definitely the way to go. This safety measure is widely known, but I feel that it is much less well known than it should be.
I see a similar issue with following hashtags. For example, I search for '#photography' which displayed a load of results across instances by said '0 posts'. I followed it and none of the cross instance hashtag results appear in my home feed.
Presumably it is only looking at the pixelfed.ca instances of '#photography' but this seems against the point of the whole thing no?
When I log in to my pixelfed.social account, doing the same thing pulls in results across different instances to the same homes screen (using the Pixelix app), so I'm not sure what the difference is.
I think proton has two levels of 'killswitch' on it's VPN. The regular one is more of a 'killswitch but only when you have the app open' while the extra options are supposed to make it an actual kill switch. Whether or not this second level is completely effective I can't say.
Binding your client to the vpn interface is definitely the way to go. This safety measure is widely known, but I feel that it is much less well known than it should be.