> so you are suggesting that one house is better than two to alleviate supply?
No, they are saying that building one high-end house still has the slightly unintuitive effect of increasing the supply of low-end homes. They also give their reasons for believing this.
i'm very aware of how filtering works in the housing market. but if your goal is to increase supply, then 2 > 1. therefore, in my opinion, filtering due to market mechanics and developer incentives is not the most optimal or efficient solution.
I'm just saying that OP didn't say that it was the most optimal or efficient solution. They were really only saying that it had the filtering effect. If your point is that we should offer incentives to build two homes and disincentives to build one home then I'm with you; I was just pointing out that you were putting words in their mouth.
