It definitely needs to be documented. But you clicked it thinking it did something, and it did something else. Just so we understand how to make this better, what did you expect would happen?

Yes I had some completely different expectation when I clicked this, but I also don't know where I got that expectation from. Also trying to explain it now is bit complicated, especially to find the right words as I am not a native english speaker.
Maybe I had a wrong meaning in my mind about what is "archive". When I think about it now, it makes totally sense when you archive the whole contact. You archive the whole contact for historical reasons and there will be nothing new. Maybe something like "freeze" I would have associated more with the current behavior, but that could also be misleading.
When I clicked that function I thought something like that I could select contacts that I would like to be archived as in "preserved" maybe. Or is that the same meaning also? I don't know, better let me try to describe it: I thought more that I would archive the old and new posts of this contact. Didn't expect it to stop receiving new items when I clicked it. I don't know why, but I thought something like it would be possible to add an expire/delete old content from DB feature, except the ones from the contacts I set to be archived or something like that.

I see it is complicated topic, also about the wording. Some explanation and documentation would be helpful for sure.
Thank you very much.