Would using PEX for potable hot water result in having Bisphenol A (BPA) leached into the water?
Does PEX have BPA content?
If it's labeled for potable water, then it (technically) meets all regulations. Whether those regulations allow for a certain amount of BPA is what you'd want to check.
That said, one should not be ingesting hot water out of the tap. I'm less worried about the pipes and more worried about who-knows-what leaching/growing in the hot water tank. Hot water is for cleaning. Use cold water for all drinking and cooking.