Hi Rene,
I can’t explain the discrepancy. All I know is that Motability confirmed everything in writing. It’s possible that they have authority to use discretion.
What I do find surprising is that there appears to be no complete written explanation on the Motability website (or anywhere else). The references to early termination are not detailed.
Perhaps if Motability put more information online (not just for this issue but others too) they’d be less need for people to go through the difficulty of making contact and their service would improve. Eight working days to get a reply, 42 minutes wait time when phoning, and not far off an hour today on online chat (mostly waiting time) is not really good customer service.