Is there any definitive proof behind that? My family too come from former Polish territories in Ukraine.
It feels like in the last decade all of Slavs have been rushing into claiming as their own many traditions. I find it sad and unnecessary.
In fact I suspect the dish to be popular to move of the former Kievan Rus' region and I know for sure potato and cheese vareniki to be very popular in Belarus and western Russia.
Yet they predominantly are served in this region so having them being “ruskie” or “ruthenian” (a huge region) is much more fair than naming it Galician.
In such Zamość region is completely removed from “Galician cuisine” mentioning Jewish, Austria, Krakow and Ukraine. Weird omission (but many regional to Krakow dishes are described as “Galician” which I suppose is a reason.
So the misattribution risk is still there due to bias even though geographically it’s correct. I’d still rather preserve name, as the more to the west the worst the pierogi gets (which is a shame).
My family comes from Red Ruthenia, region where ruskie pierogi comes from. Because of lingual characteristic they are usually linked to Russia (as mentioned in article) and so, with all the turmoil many restaurants decided to rename them: either to pierogi with potatoes and cheese or to galicean - as from Galicia, which is commonly perceived as Krakow (due to it being center of the region).
Krakow doesn't have as good pierogis (but there are other things worth seeing and eating there though) and is half-the-Poland away so it feels to me somewhat like a takeover of a legacy and stings. So if you ever have a chance - go visit Lublin or even smaller cities like Chelm or Zamosc. Food is absolutely terrific there (which I guess is thanks to charnozem soil [1] in the region).
[0]: https://en.wikipedia.org/wiki/Galicia_(Eastern_Europe)
[1]: https://en.wikipedia.org/wiki/Chernozem