I agree with that.
Dakar bikes are built and re-built each night at the vibouac. Is not a trustable endurance reference. Even in the marathon categorie you can change most of bike components every night.
Long range or short range adventure bike could be the issue here. IMO is about the kind of terrain you are going to find on your trip.
In my case , for Morocco, when i search a hard ride on any kind of terrain available there (sand, camel grass, stones, oueds, etc) i use de 525 that i carry to there on my 4x4. On the other hand , when i search to cover long distances following roads, country roads, tracks, "pistes", etc....., y go with the GS1200ADV.
It is just about using the right tool for the right job.
11´ BMW R1200GS ADVENTURE
09´ KTM 530 EXC
06´BMW HP2 ENDURO