Grimdark fantasy novel has got me curious about race and penis size... lemme explain

All right I know the title is weird but hear me out. I'm currently reading Dragon Republic by R.F. Kuang (second book in The Poppy War trilogy; highly recommend but check trigger warnings first) and came across this passage:

“Have you seen their penises?” Kitay asked. “What?” Rin nearly spat out her fish. “Hesperian men are supposed to be much, ah, bigger than Nikara men. Salkhi said so.” “How would Salkhi know?” “How do you think?” Kitay waggled his eyebrows. “Admit it, you’ve thought about it.”

It got me thinking—there’s a lot of talk in the book about differences between the Hesperians (aka Westerners) and the Nikara (inspired by Chinese culture). I've always heard the stereotype about Caucasian men being "larger" but it made me curious: is there any truth to it in real life?

My best friend is an Asian guy, and he’s always been open about things, but I’ve never really asked him about this topic. I’m wondering if other people here have thoughts on whether these stereotypes about size actually hold up in real life—or if they’re just myths.

To be clear, I’m not trying to make anyone uncomfortable or reduce people to stereotypes—I’m just genuinely curious after reading this book and having conversations with my friends. Has anyone had any personal experiences that might shed some light on this, or is it all just a bit of fiction and folklore?