If you read the list, there are many dozens of disability aids on there.
Maybe, Motability don’t consider that things like Special paint and ultra-low-profile tyres/wheels are a ‘necessity’ to warrant inclusion on the list.
However, when it comes to ‘winter packs’, I’m sure their response would be to look for an alternative vehicle where it is included.
Hardly discriminatory.
If it doesn’t suit – don’t join the scheme.