What you're referring to, is the allowance to subdivide a lot to allow for a duplex / attached home (33.110.240). 

In the case before us, if a 5,000 sf lot is now zoned for R7, you wouldn't be able to make use of that exception as the original lot + new lot created would not meet the minimums under 33.610 Table 610-2.

Roughly speaking, the ability to build a duplex / attached home under 33.110.240 is taken away.