If it's a worn out belt, then the speed should be slower, right?
Anyway, I have solved the problem. There is nothing wrong with the PL-41. It appears that my reference turntable (Hitachi Lo-D) was the one that was wrong, since I didn't follow the strobe and just placed the pitch at the middle of the dial, thinking it was the correct setting. So, it turns out my PL-41 was right all along. Hehehe.
But my other TT, a Kenwood, is the one whose pitch sounds wrong. That might be solved with a belt replacement.