if you scroll down to chatty you will see, that you can add your own Id (of whatever server).
For me that’s the only reasonable thing, binding someone to your thing against your freedom would be google-alike in my point of view and having me deeper concerns than some timeline moving ;-).
However even if they would do so, the apps have at least for me the objective to serve together as a PoC that linux (not only pureos - but linux) can do mobile. Binding to one service already would be against this objective and also harm the platform, as pureos benefits in case linux mobile grows (also with competitors like pinephone etc).
I guess that by your question you have a similar opinion 