Actually mentioned I2b is a mtdna(maternal), not Y-chromosome(paternal) thus the smaller percentages. So it would be opposite of what you said, it would indicate if Lemkos, which are one of the possible descendants of White Croats have I2b, it would mean that I2b along with R1a was an Croatian genetic makeup early even from those times when we were East-Slavs. There's a strong hp I (both maternal mtdna and paternal y) in Ukraine and Moldova, and Carpathians in general.
The fact that mtdna(maternal) I was found in Carpathians, in same high amount as in present day Croatia, island Krk, is of big importance. Because, it means families, women, lived there. It wasn't Croatian male warriors or something like that spreading the gene, but it was settlements with both males and females living there…which further collides with theory of our migrations from east to west only this time it indicates that Croats of hp I and hp R1a both migrated together towards West…
Further more to continue this puzzle, Croats arrived in Croatia in two weaves, first to Dalmatia than in Pannonia.
In 550. roman historian Procopius said that when Croats arrived to Dalmatia that savagely killed over 4 million people of Dalmatia (my guess latins i.e. Romans?), which in that time that would have been around the whole population of Dalmatia. And considering that the first weave of Croats arrived there in Dalmatia in that time but they carry hp I today, it would mean maybe that Carpahian/Ukrainian hp I White Croats(Sarmatian/Slavic) massively arrived to Dalmatia and conquered it according to historian, while R1a White Croats from present day Poland arrived in a second weave settling Pannonia and merging with White Croats from the first Ukrainian weave.