For most Polish people this would be quite an insult even disregarding current war waged by russia just next to them, which is pretty much impossible to ignore if you live there.
Clearly.
There is plenty of information regarding history of Lviv and this region in general. It's long and sad, tragic and sometimes beautiful but never simple.
Besides, I found that most people who feign ignorance know history very well and use it for their own agenda. If you know what to search in someone post history it becomes more or less obvious.
In reality, for as late as 1939 the main differences were language and religion, and considerable chunk of rural population considered themselves "locals" not linking with nation-state idea.
This reflects on Commonwealth being rather multi-ethnic and Austro-Hungarian occupation and repression changing little on the areas they took.
Modern states in the region are real, but contingent, and shouldn't falsely be projected backwards through history.
The phrase "Soviet Writer" can be treated more loosely though and can be taken to embrace those that wrote about or had their writing influenced by Soviet events and it's difficult to imagine Lem not being aware of nor affected by the social upheaval radiating out from the formation of the USSR.
His identity is Polish, his writing contains elements that stem from | react to Soviet history and culture .. it's hard to write and not be affected by loud neighbours that raid your kitchen and stomp on your belongings.