This legislation will be tough on the new build investors that buy, build, and sell SF homes. Quite a hit to the shorts for the only remaining vacant lots left in developing areas. Those are areas primed for new construction with a huge number of RSA5 lots on 14x50 sf (exactly 700sf). If people own land or need to tear down their property now and build while they can still lock a 38ft building in place. @Dan Powers the minimum lot square footage for RSA5 properties is still 1,440sf not 960sf with 16ft of frontage if you are looking to subdivide without any sort of variance. Getting below 1000sf is usually only a special exception that depends on 75% of your surrounding lots being less than 1000sf specifically designed for large parcels that are surrounded by smaller lots so city can keep consistent density throughout the block.
See the image below of the remaining RSA5 vacant land parcels that risk getting rezoned to RSA6 and can only have two stories built on it.
Although it does seem like the city is trying it's best to get into developers ways, there are some council members that still support development. This one does not actually seemed directly linked to the Strawberry Mansion piece, they are supported by two different council members (Mansion rezoning by Darrel Clarke, new RSA6 zoning by Quinones-Sanchez) that likely are affecting two different areas. Quinones-Sanchez is actually rather developer friendly (Clarke is not), this may be a balancing act for her constituents since she has been able to pass some investor favored overlays recently. Notice how a large portion of small vacant land falls within her district. The RSA6 zoning does not have anything to do with roof-decks, building materials, or having a homogenous look like the bill for Strawberry Mansion Rezoning. Interestingly, there are no lots that are <700sf in the area that Darrel Clarke imposed the new building restrictions.
If you want to follow how the city is making its way more and more into real estate, I would rather follow how council members are LEGALLY starting to take over more influential roles as "city planners." This is where you'll start to be able to predict what areas will become more difficult to build in, and those that wont.