Because I see a difference between 1) "rezone all houses to be boarding houses", and 2) "rezone to allow all houses to be boarding houses". The first one sound

Because I see a difference between 1) "rezone all houses to be boarding houses", and 2) "rezone to allow all houses to be boarding houses". The first one sounds like a require, the second sounds like an optional. Like, "rezone all houses to be agricultural" would be a very different than "rezone to allow agricultural use." That link you pointed to wants to prohibit group living arrangements ("the loopholes [that permit group living arrangements] are still there. A few simple amendments can, by eliminating the loopholes, insure effective zoning"). It's absolutely does not want to rezone to allow boarding houses in R-1 single-family zones.