Let's hope they mention cortosis next episode but I doubt it will happen. They handwave a lot in the SW shows these days and expect the audience to know everything. Ahsoka was a prime example. The live action audience had never met the Rebels and they had no reason to care for them and the show seems to want to treat the audience as if they knew all about Ezra, Sabine, and Hera.
You're conflating two different phenomena.
Re: Ahsoka your claim is correct. The show didn't set up much, didn't explain the characters, didn't really do much at all to help anyone new to the characters. It essentially treated itself as an extension of Rebels, and yes, as you say, according to Disney and others, most people who watch the live-action shows haven't watched the animated ones, so that's just bizarre behaviour by Filoni. Most of the big emotional moments in the show just do not work
at all unless you watched Rebels. It's just a succession of wild things happening.
This is something very different though - it isn't expecting people to know something long-established and detailed in other media - it's a single simple thing about the equipment one character has that they're expecting audiences to go with the flow on.
Knowing what cortosis is allows you to name it but it doesn't aid your understanding of what is happening significantly (esp. as cortosis in the books is inconsistent in what it does). Like others my initial thought was he'd damaged their lightsabers, maybe with his - only when it kept happening - and you could see it was when he used his bracer (or seemingly his helmet at one point) did I realize what it was. But if I didn't know what cortosis was I'd have thought "Whoa his bracer shorts out lightsabers!".
Conflating these two different things does no-one any favours and seems ironic when you're moaning about education, because this sort of conflation is precisely the sort that good media literacy avoids.
Who is arguing in bad faith?
The most likely answer is they either forgot to include a quote to something from significantly earlier in the thread or are talking to someone we both have on ignore (and/or who is ignoring us). Because that doesn't seem like a response to anything you or Paul said.