This is the difference between “council tax” a tax on property and “poll tax” a tax on individual people, and that went quite badly when it was tried... So it makes sense for the primary accounts to be per property. However you are quite right they should have a better understanding of a second layer of accounts being individual people.

The IT infrastructure around tax/HMRC is ridiculously complex. The “making tax digital” initiative is trying to fix that. The aim for business taxes, for example, is that each individual business will have a single tax account eventually, rather than separate once for each tax type as they currently do.