It's the exact chord progressions the entire song - which is fine, happens all the time. But when you the fact that the vocal melody on the chorus is identical as well - well it's then it's completely obvious it's a rip off.

It's the identical chord progression the entire song (instruments) and chorus melody (vocals). Hardly an accident.

A similar riff? OK that might be a "music accident". The identical chord progressions along with the chorus vocal melody? Yeah not so much. Kudos to the legend for being chill about it though.