@kirby
It had worked exactly the same way in Skype, even the video calls had been p2p, I'm not sure if it started with MS acquisition or earlier, but they began phasing out the p2p parts at some point — but even when it was Microsoft already, file transfers were still direct, they weren't uploaded anywhere for the other party to download it, one party initiated the transfer, the other one had to accept and choose the directory to save the file in, I don't remember when everything started to get uploaded to "the cloud", but AFAIR, not even that long ago, less than a decade.
@tk