"Standard" implies a lot, and definitely there is nothing about "enabling two-way communication between willing participants" that requires "make available a video on the screens of my contacts in a non-directed way" to be part of the offering.
Signal is not social media. That is not its intention, nor its purpose, nor even its design. It is a messaging service. We already have a discovery feature in Signal: using your contacts, you can see who has Signal installed or not.
This feels like bikeshedding to the max, because it is.