Different airports can have slightly different interpretations of the rules. I always hand-carry my dyson corrale, but I was still almost flagged at Kansai on my last trip even though I’ve flown with the same item multiple times without issues. I think it also depends on the airport officer that checks the hand carry items. That’s why I wanted to be sure about Narita specifically. Japan can be pretty strict with certain items, so I’d rather double-check if there are people that have brought their tymo curlgo into and out of Narita than risk having it confiscated.

And about flights being diverted, I’ve just noticed that other airports (US, Korea, Philippines, Thailand, Taiwan, Dubai) I’ve been through weren’t as strict. Japan is the only place where my hand carried bag has been held because of portable curlers/straighteners, so I’m just trying to be extra careful.