Band A houses are usually pretty small, so this just a reprise of the argument that has been trotted out several times on this thread about studios and two bedroom flats. Since it’s you, though, I’ll assume it’s being deployed in good faith.
I am not suggesting that anyone in Band A downsizes. Why would I?
The heftiest council tax bills, where 25% discounts make the greatest difference, apply only to the largest houses - which it could be argued should really be occupied by families, given the general shortage of housing. In these cases, of course, equity easily funds the moving costs and stamp duties.
Single people - especially the widowed elderly - have a perfect right to occupy very large houses that they feel comfortable in, but it’s reasonable to question property tax incentives for this choice.