I answered your question. I just provided the link and quote for context, since v102 incorporates breaking changes to the .sketch file format. The real-time part of the quote was just part of the banner notice from the link, so I included it.
I guess I should note that beta software is unfinished, and by virtue of that fact compatibility with future versions of that software cannot be assured, even by the developers. That said, it’s standard practice to attempt to ensure compatibility between files of a beta and production version of a software, unless explicitly stated otherwise.