Thank you for the revelation
Thank you, Doitsu, for explaining this to me. I have been misled for years, because putting chapters in the <guide> in content.opf actually makes the GoTo in Kindle Previewer let you go straight to chapters!
I realize now that this has no effect on the files as read on devices. My mind is blown.
Thank you, thank you, thank you.
Any idea why KP displays this stuff?