This is behaving as designed, but it seems off because we're using Community Events a little weirdly.
Community Events are supposed to link to events a community might be holding - chat events, hackathons, question contests, etc. That's why they have the favicon from the same community they're on. That's the part that's status-bydesign.
This Community Event is a little different, though. We manually added the Developer Survey as a Community Event on Code Review and other code-related sites. This is because the only way to get a meta post to propagate to other sites' Community Bulletins is to post it on MSE and tag it featured. But the survey is strictly developer-related, so it didn't make sense to put it here and link to it in Community Bulletins on SciFi or Writers or Beer (as examples). So we posted it on Meta Stack Overflow, and in order to get it into only certain Community Bulletins, we manually created Community Events with a link to the survey on all of the non-SO sites that we thought might care about it.
(The other alternative would have been to create duplicate meta posts on each of the target sites, but that is not desirable because it decentralizes the discussion (bugs/questions/etc) about the developer survey. It was deemed better to have it all in one place.)