Signal is actually pretty good for the occasional "cross-iOS/Android" video chat. Can't use iOS Facetime, don't want to use $META, google/meet is OK, but isn't quite as straightforward as "@Signal => CALL_ME".
That sounds like a bad joke. "Everyone can use Facetime, except if you're on a certain platform you have to ask someone on the 'real' platform to initiate the call." That's... not a viable communication method.
Almost all links I get via SMS are phishing. The rest is OTP, there is sometimes a link in the same SMS but I _never_ clicked a link in an SMS...
My point is, the inhibition to click a link inside an SMS is very high with lots of users, hence I can't imagine this working well.
Also, it's purely inconvenient. You're not having a conf call at a previously agreed time, you want to call someone, this means it's spontaneous or somewhat urgent...
Most people lead up to an invitation to a video call with text messages (e.g. "When are you free for a video call?") unless they're very familiar with the other party.