It’s not the first time I’ve seen this discrimination and having little use of my left hand and leg I’m able to use a mobility scooter with no problems but unable to use a wheelchair unless its a motorised one.
I think if I remember right that even HMG does not recognise scooter users as disabled as they too always refer to wheelchair user and indeed all the parking spaces we use with our blue badges have an icon of a wheelchair in them so its kind of suggests that if your disabled your a wheelchair user.