These two guys* were crazy productive in the 2 months they worked. Just the level of commenting shows how much thought they were able to give it during that span.
* plus the math package guy
I checked the documentation and looks like even the 4K version supports single precision floating point numbers (32-bit). Not sure how they managed to do it in 8-bit machines but I guess they just had to use more registers/memory for each of them.
2 months to write a working BASIC from scratch in the shared computer environment seems highly unlikely. I think more time would be required and having some source to inspire and guide the design would be a big advantage.
Does the code work?
I.e., has anyone OCR'd the listing and fed it into an emulator yet?
I always thought that the floating point routines were the big feature that made Microsoft BASIC a thing (compared with both Radio Shack and Apple integer BASIC). It's interesting reading about Monte Davidoff and also that Gates knew they needed a specialist for this.
https://en.wikipedia.org/wiki/Monte_Davidoff