It rests entirely on the presumption that thousands of non-piggs like your example from above (that could care less about all the charts and trending) do not exist in the world and won’t snag your dream house out from under you before it hits yours dream price.
Actually it rests on the assumption that they won’t be able, which is why prices fell in the first place. People would still love to buy, they just cannot afford it. So piggs are the people who saw this coming and saved accordingly. Sure there are non-piggs doing the same, but not a lot.