YouTube has A/B testing features that allow videos to have multiple titles and/or thumbnails.

Right. So I thought it would be helpful to share the more-descriptive title that I got.

This is what I use DeArrow for, crowdsourced titles and thumbnails (from the maker of SponsorBlock): https://github.com/ajayyy/DeArrow

I'm sorry, what? Can people now see different titles? Insanity, if true.

It has been that way for a while now. I see Veritasium video titles and thumbnails change quite often, it can be quite annoying as it sometimes gives the appearance of it being a whole new video.

A/B testing a title feels wrong to me, its almost as bad as A/B testing a UUID. Just pick a title and stick to it unless you need to fix a factual error.

Titles and thumbnails have a huge impact on video performance, and when it's your main income it seems reasonable to try to marginalise the impact.

And video performance = ad revenue.

Oh yes. Some channels cycle through many different ones as they test them. Veritasium is notorious for this.