While looking for reference to kpzbg1.exe, I noticed that the tp2 file references two times "castilian" in the language check to determine the name of the main character soundset files imported from Baldur's Gate.
In line 9194 of setup-bgt.tp2 (for BGT 1.18), I believe the test should be made on "polish" instead. According to comment on line 9355, polish is among the language handled but it doesn't appear in the various language checks in that part and castilian appears twice. Since hembra is indeed a spanish word, I believe "castilian" test is right on line 9113 and wrong on line 9194.
I believe the polish soundset from BG1 are not available in BGT due to this mistake, more specifically that the player can't choose bgmale[123] and bgfeml[123] as soundset for the main character when playing BGT in polish.
The sound files that would be copied are named on[123]* and ona[123]*. I believe a polish player could confirm that these names are indeed used in the polish version of BG1.