I have a new pet peeve (or hobby horse?) - the verbal tic when people introduce an explanation of something with "For those who don't know…"
I think I can see why the speaker would say so - it is used as a sort of acknowledgement that you're now explaining something to people that they already know. Sort of "Sorry, but here I go anyway, just to be on the safe side".
However, to the person listening, it easily sounds very different from that.
If you are one of the people who know, then getting a relevant introduction to something you already know as part of a story isn't something the speaker has to make excuses for. The introduction will serve as a reminder, the person who knows can check that they remember the basics right, and it will also serve to align terminology. As the speaker has prepared, the speaker will almost always know the specific subject the best.
If you are one of the people who don't know, then it is easy to hear "but you should" and "but you don't, so now I'm going to waste everybody's time to bring you up to speed," even if it wasn't meant that way. Learning something when you've just been singled out as behind and lacking is not effective.
If the introduction is relevant, short, precise, and fits the narrative, include it without a disclaimer.
If the introduction isn't necessary, skip it.
Don't make listeners feel bad.