That seems to be available, though?

https://call.element.io/meetingwiththegang opens a meeting for a room named "meetingwiththegang".

Ideally, you'd want to use such a system with accounts so you can apply some kind of ACL, but if you want to use randomly generated room names for secret links then everything you need is there already.

Looks like you can't change the room name after starting the call, but you can start a new one at the new address if you want to change the name.

I think it does in theory (Matrix supports changing room addresses), however what is the benefit of this as opposed to using the same address for all meetings?

I think that's what they want, I believe by "changeable" they meant "customizable"?

The person you're replying to wants to set it to something custom, to make it memorable and meaningful.

We have this today. https://call.element.io/whateveryouwant does what you'd expect.