It doesn’t say anything that I noticed about it being a guard discovery attack. In fact it seems to indicate that it was just plain end to end correlation. I mean, yeah, that discovers your guard, but not in a way that vanguards are going to do anything about.
It’s true that, if I remember right, a lot of really suspicious nodes popped up on the network around that time, and maybe it was guard discovery by stimulating traffic. But it’s also true that, if you’re Germany, I’m not sure you need to run any nodes.
The network as a whole is worryingly easy to watch. And when you don’t really know what’s going on, it’s not necessarily the best idea to tell people to go ahead and do whatever because “it was just old software”.
Anyway, did ricochet embed its own Tor at all? Vanguards are a Tor feature, not a client feature, are they not?
… although another thing to do might be to add, and actually use, a self destruct for old versions of both classic Tor and Arti. Including the embeddable versions.