No, sorry, this was told to me by a Korean colleague years ago. IIRC he said it was mostly black pepper but sometimes something closer to Szechuan pepper, which

No, sorry, this was told to me by a Korean colleague years ago. IIRC he said it was mostly black pepper but sometimes something closer to Szechuan pepper, which Wikipedia tells me today is probably https://en.wikipedia.org/wiki/Zanthoxylum_piperitum https://en.wikipedia.org/wiki/Zanthoxylum_piperitum. His claim about napa cabbage is easy to verify (and of course daikon and other vegetables are are still very common in kimchi, so it's easy to imagine kimchi without it) but I can't any more details about the supposed black pepper version.