Sounds more like - we don't want anyone to know it's a ghost town here (metrics will prove protestors correct) - so let's say it was a system down issue - and then claim there was no meaningful protest.
Reddit faked their initial users to make the site seem used. Pulling the plug during protests surely is in the realm of possibility for what they could do.
1.2% of subs does not imply that 1.2% of the user base is gone. A lot of those 500k subs have less than 5k subscribers. Only a small portion of subreddits contribute to the vast amount of content on reddit.
It's likely true that most people just browse, don't login, and don't subscribe to subreddits they enjoy. Of course those people don't contribute to their site either, although they do see the advertisements.
Anyway for those of us that do login and follow specific topics, I can speak for my own experience, which is that every single subreddit I read was shutdown this morning other than r/worldnews and r/diablo4.