~~Can you send us an example of such a post as you are talking about? B/c I am not seeing it.~~ (Edit: oops that was old and I forgot to remove this sentence - see below.)
The most recent content on lemmy.blahaj.zone that I see from sh.just.works is from 2 hours ago: https://lemmy.blahaj.zone/post/1688895/11494679, so those two definitely are federated (I checked and don't see either one in the others' instance blocked list). However, as expected the user https://lemmy.blahaj.zone/u/CDRMITTENS@sh.itjust.works has no content more recent than 7 months ago. They both say that they are running the same Lemmy version - 0.19.5.
Searching... seems not to work for these style of posts, b/c while the searches pull up zero results for common things like a single space, a colon (inside a URL?), the single letter "a", etc., there actually are such posts, e.g. https://sh.itjust.works/post/27811262.
Also, !noncredibledefense@lemmy.blahaj.zone only has 10 posts total, but none are from cdrmittens.
So yeah I think you are correct - the old content that was already there in Blåhaj Lemmy's database remains, for their content posted to !noncredibledefense@sh.itjust.works, but after the ban anything that the Blåhaj Lemmy tries to pull in for that user just gets discarded, and not added to the database. i.e. it has the old but not the new content, for that user. Most likely votes as well as posts or comments (b/c why would that be different?). Though since !NonCredibleDefense@sh.just.works has nothing to do with lemmy.blahaj.zone, they can continue to post on their own home instance - it is only Blåhaj Lemmy that will not see those posts, by design, b/c of the ban.
I hope that makes sense!:-)
Not... entirely. In March we had 54k Monthly Active Users, while now we have only 45k, that's a not-entirely-insignificant drop of 17% of users. Also, personally I've created some alts during that time-frame, so if others did similarly... the real drop could have been much larger.
Ofc, it could have been that people simply dropped their older alts and are now happy with fewer alts but the same number of people - but that gets to that very old argument that Galileo had with others about whether the moon was perfectly smooth (due to spiritual implications) or not: he observed that it was not, though others raised their objections and tried to counter with the notion that perhaps there were mountains on the moon... but that if so, surely the valley regions were covered with glass, so that the moon retains the property (again, for reasons of spiritual purity) of being a perfectly spherical object?
Ofc you can guess what Galileo said to that: surely there must indeed be glass on top of the valley regions, so that they fill in the height of the mountains with an equal height of the glass valleys, which we cannot see b/c they are made of glass, , yes indeed "surely" that "must" be the case - but also, in addition to that, there is EVEN MORE glass on top of the mountains, height proportional to how tall they are, and while we cannot see that material either, that is what is causing the differences in shadows, which he could measure with his spyglass that he pointed upwards into the heavens.)
Moral of that fun story: we can conjecture such matters all day long, and how fun that would be for both of us! But at the end of the day, all we have are the facts and numbers in front of us, however imperfect they may be:-).
That said, these numbers may particularly be bad, e.g. if anyone left Lemmy and went to Mbin and/or PieFed, then I think they would not be counted in those charts? I am not 100% certain about that, or much of anything really, but pretty darn close b/c of how the "software" field seems to work on that site, with the other buttons like List and on a particular chosen instance to look at more details, the Main Data tabulation (and see e.g. https://mbin.fediverse.observer/piefed.social, click to expand the Main Data, and that JSON output has "softwarename": "piefed", but nothing at all with the text string "Lemmy" there).
The total number of Lemmy instances has also dropped 24%.
Although the total number of both posts and comments has gone up rather than down - so we see a lot more activity, from a significantly smaller number of people. I wonder how sustainable that is though, e.g. next year won't be an election year in as many countries as this one was. Overall I am worried about the health of the Lemmyverse, though less worried than ever before about the health of the overall Fediverse b/c of the newer software alternatives that have and are still coming:-).