Those first-time buyers won't be able to afford the houses that the pensioners leave, anyway. They need first-time houses at a price that doesn't mean they can only eat bread or baked potatoes for the next twenty years. The ones who buy the pensioners' family homes will be middle-aged couples whose parents have died leaving them a share in their family home (with their sibling(s) getting their share too) and as a consequence they are able to upgrade to a similar sized home themselves.
Oh, no, I forgot. Their parents will no longer have the family home to pass on (or the value of it - that will have been spent on buying the downsize house, outbidding a first-time buyer. Anything left over will be needed to buy care), so the middle-aged won't be able to upgrade, so won't be able to sell their current home to younger people looking for a stepup home who won't be able to sell their starter home to a first-time buyer.
Does he not know that any item sells for as much or as little as someone will pay for it? If no-one can afford it and there are no similar others available at a lower price, it remains unsold, and the price drops. Supply and demand. To make the average price fall, increase the supply available, or increase the availablity and attractiveness of alternatives, such as social housing rentals, and don't sell off LA housing stock at laughable prices without replacing each unit that leaves the national rental stock.