It's an in-demand cultural speaking affect for those in the service industry or doing public narration - whether it's in Japanese or English. Think of it like Chick-Fil-A's policy of saying "my pleasure". Also, as a native English speaker you will notice your natural tone and accent change after years of living in Japan - though not necessarily in this exact style.

It sounds almost exactly like that female AI "tik tok voice" that's often found narrating some crappy short video.

This voice too may very well be AI. Nowadays it's really hard to tell.

I assumed it was a computer voice. Does anyone have an example of an on-camera human speaking that way? I think it'd be very off-putting to hear someone speak to me like that in person.

I've definitely heard intonation like this from before computer voices were of this quality. I don't know if I've seen an on-camera human speaking this way because it's often narrators or English dubs of Japanese content.

I hate that voice so much. So many videos that are just a vapid TTS reading some ChatGPT-esque summary with some stock footage but you only find out that's what it is after the unskippable advert.

IMO it's a mix of tempo, lack of a proper pronunciation training (and it's harder for them) and a pinch of keigo.

To save others from having to look up, "keigo" is roughly translatable as "formal (as in etiquette) language"

That style of narration is what I'm accustomed to hearing in children's programming in the USA. I've often found Japanese English-language productions rather irritating because the script and narration style seem targeted at 5-year-olds.