Uh, not really? They have to stay there anyway for SB9 - this gives them a tractable (aka actually) doable way to get more wealth now without having to leave, and still retaining their home as-is in many cases. And it means SB9 like densification and additional housing is more likely to actually happen.

99% of homeowners could not actually do what you need to do for this densification - the planning, paperwork, and execution to get everything done is very difficult. 20% of net profit in exchange is pretty good actually. You’d need some truly crazy levels (several million+) of pure gain before it would make sense to try it yourself IMO.

I’ve done a decent amount of permitted work and far smaller projects can easily burn a year of nights and weekends.