I don’t think the reason was technical. Firefox has supported WebM (a subset of Matroska) for 11 years, and whatever code they had probably would have been enough for most Matroska files, assuming the codecs are also supported.

However, Matroska itself was only officially standardised last October despite being in use all these years. That was probably what convinced them to add support.

Their blog has regular updates regarding Exchange support, if you’re interested.

It doesn’t launch the new binary at all. When the current process wants to create a new process, instead of doing fork+exec (which launches the new binary and wreaks havoc because versions now don’t match), it simply tells the ForkServer (a different process running the old binary) to fork (split) itself.

Chromium also does this; they call their equivalent to ForkServer the zygote process and this article explains it really well.

All external links from news.itsfoss.com articles have that ref parameter added. For example, see the links in this article about the Danish ministry that is switching to LibreOffice.

Edit: This is apparently something that the CMS they use, Ghost, does by default.