It's probably Microservices(TM)... The black box responsible for rendering the HTML is some other black box to the UI or whatever. The UI offers you locale options, but the renderer that fetches video titles hasn't been configured to respect this, probably uses locale from geolocation and some overpaid genius said "always use machine translation if locale doesn't match video title language"...
The homepage of google.com is also localized. I remember noticing that even when requesting and getting the English locale, the tooltip for the doodle was still in my region's language... wahey!