It doesn’t, you aren’t compelled to use Signal, I care that the clients I’m talking to are conform to the spec and don’t expose myself to side channel attacks (e.g. previewing content directly from the client)

Fortunately, I'm not. But due to the nature of messengers, I likely would if Signal became popular.

If you don't want others to use a client of their choice for some (real or imagined) security benefits, that's between you and them. I think most people will think your priorities are silly.