Naive. What actually happens is that landlords who have hitherto been content to let to tenants with weak credit ratings (and whose rent is often paid directly by the local authority) serve section 21 notices before the deadline, and evict those tenants. The properties are then either sold or rented to young professionals with much better credit ratings and higher income. Generally the occupation density falls for these properties at the same time.
It may be different in Derbyshire and other northern counties, but the above is exactly what is happening in the London suburbs. I have close personal experience of exactly this in Bromley, Lewisham, Greenwich, Peckham, Blackheath and Dartford. Rental agents are, discreetly, actively suggesting it to Landlords as their incomes also depend on rental values and they want to rebalance it before labour get their policies enshrined in law.
Same number of homes in the market but it is disadvantaging the very people labour says it is trying to protect.
It will be interesting to look back in say 3 years and find out whether it improved matters for the poorest tenants, or made their lives worse. Developers are not going to fall over themselves to build affordable social housing either.