The adaption I use are electronic remote control devices so can’t comment on left foot adaptions but only advice I can give is to take the car to a different adaption installer and ask them to check it out and that’s its up to being safe to use.
I’ve done this myself in the passed when one adaption installer told me the hoist I’d ordered was no good and that I needed a more expensive one. I contact another installer a hundred miles away and not telling them why I was asking I just told them of the two hoist models and they came to the same conclusion as my local installer that the cheaper one was naff for the car it was going in. Doing this is a bit like you don’t have to have the car serviced by the dealer who supplied the car so goes with adaption installers too.
Sorry I can’t help any more than that and as far as Motability are concerned to me and other here, they seem to be lately just passing the buck to everyone else and not fighting the corner for their customers, maybe there being influenced by our wonderful government or working from home too busy watching the latest Netflix series.