Part of the reason Youtube provides the youtu.be link is that their systems disambiguate between mobile and desktop websites. Mobile versions have the 'm.' sub

Part of the reason Youtube provides the youtu.be link is that their systems disambiguate between mobile and desktop websites. Mobile versions have the 'm.' subdomain, and provide a less optimized experience for desktop. I would also argue that the youtu.be link is a canonical form, since the identifiers are identical to the source. It is just an optimized canonical proxy.