This isn’t a policy, it’s just documenting something.
If you are in a room and want to send it to someone and pick “Copy Link” from the invite menu, you will get a link like this:
If you follow that link, you’ll be invited to join with various clients, but none of them are the chat.fedoraproject.org web client. But, if you add
?web-instance[element.io]=chat.fedoraproject.org to the end, et voilà.
I have an issue in with the Element Web project to make these links be the default (Allow "copy room link" to get a URL from our web client to point people _back_ to our own client · Issue #19082 · vector-im/element-web · GitHub), but I don’t think that’ll happen soon. So in the meantime, make sure to add the magic incantation when sharing links (and especially when documenting them).