he/she is wrong i think
from the horses mouth
What dwellings are exempt from the tenancy registration system?
Business premises, even where partly residential (to which section 13(1)(a) of the Landlord and Tenant (Amendment) Act 1980 could apply).
A dwelling to which Part II of the Housing (Private Rented Dwellings) Act 1982 applies (i.e. formerly rent controlled dwelling occupied by the “original tenant” or his/her spouse) or to which Part II of the Landlord and Tenant (Amendment) Act 1980 applies (i.e. long occupation equity lease tenancies)
A dwelling let by a local authority or voluntary housing body
A dwelling occupied under a shared ownership lease
A holiday let
A dwelling in which the landlord is also resident
A dwelling in which the spouse, parent or child of the landlord is resident and there is no written lease or tenancy agreement
A dwelling that is occupied rent free
If a dwelling is available for renting but has not yet been let, there is no requirement to register.