Szeged is a fairly large city and has a lot of names standardised, for example Segedyn in Polish. Why would the German name not qualify there?
It’s not marked on the city limit signs, no German speaking minority lives there anymore, and non-local German speakers started to use endonym of the city. That’s why.
It doesn’t affect the Polish name, it’s just how German speakers call it, these medieval names sound archaic for them.
But you can read the thread you are replying to, you can find a lot of reasoning up there…