Ummm no... Look at Lviv, Brasov or Cluj for example and remember those were the largest cities in their respective regions.
...and
then you remember that a) these linguistic boundaries will often have been more complex (and often to the point of making a mockery of the word 'boundary') at a local or even regional level, and that b) a very large ethnic group in the area at the time is not included on the map (Jews). And that there were other ethnic groups not denoted either (Roma, of course, but also Rusyns and so on).
Let's take the city marked on the map as 'Lviv' as a totally unrandom example. Majority Polish (so Lwów), but Jews, not Ukrainians, were the second largest group - over a quarter of the population - (so Lemberg over Lviv).