I don't have a source either, but I can confirm having heard the same advice.

In general, even if uBO has been updated to avoid Youtube's adblocker-detection, if you're running multiple adblockers it's possible the popup is triggering because it detects the other one.

More to the point, (a) you shouldn't need another adblock alongside uBlock Origin anyway, and (b) pretty much every ad-blocker other than uBO has sold out and been compromised, including Adblock, so using it is a bad idea to begin with.