This is probably not a coincidence or an oversight, but rather a "what can we get away with" attempt, similar to previous efforts to remove UBlock Origin.
But why? Matrix is tiny and no threat to Google services.
I'd personally expect three letter agencies to be involved here. The US government has been aggressively going after encrypted communication for years, with extreme tactics like personal intimidation and secret courts. Read this story about a secure email provider if you doubt it. [1]
This doesn't work so well with EU based companies, even though they have been pushing EU governments to do the same. (There recently was a leak that the encryption ban currently discussed in the EU parliament has some roots in Five Eyes efforts and that governments were pressured by the US to support it. Published by FAZ or Sueddeutsche, I'm trying to find the article...)
I also doubt that iMessage and What's App gaining "backdoors" to their encryption is purely motivated by user experience.
At a time where a lot of people want to switch communication platforms, nipping any such efforts early might well be viewed as important.
"Abusive content" is a convenient excuse that can be arbitrarily applied.
[1] https://www.newyorker.com/tech/annals-of-technology/how-the-...
