nope there Ukrainians in Poland
I know there are many Polish-Ukrainians but the 2 or 3x increase must be due to immigration.
Rocznik Demograficzny [stat.gov.pl/gus/5840_rocznik_demograficzny_PLK_HTML.htm]
en.wikipedia.org/wiki/Demographics_of_Poland#Ethnic_groups lists born in Poland and foreign born residents by ethnicity.
Polish 96.5%,
Ukrainians - 300.000
German 152.897
Belorussians - 80.000
Armenians - 50.000
Vietnamese - 45.000
Tajiks - 32.000
former Yugoslavian - 29.000
Greeks - 25.000
Iraqis - 21.730
Pakistani - 16.846
Russians (including Chechens) - 16.550
Uzbek - 15.389
Spaniards - 13.481
Mongolians - 12.251
Chinese - 11.272
South Koreans - 9.905
Kazakhs - 9.479
Turks - 9.371
Romanians - 8.740
Irish - 8.655
Lithuanians - 8.639
Somalians - 7.864
North Koreans - 7.196
Ghanian - 6.368
Indians - 6.606
Libyans - 5.601
Bulgarians - 5.482
Japanese - 5.329