Have there been any steps to address this attack vector using geofencing or rate limiting?
This doesn't really seem to be an attack vector that is of consequence to most users. While the paper claims to be able to sense people in the enviornment "through walls" - it is based on a pretty idealized set of conditions and assumptions.
But... You can already do geofencing by simply reducing power levels.
And regarding rate limiting or signal obfuscation that is mentioned in the paper -- those would come at the expense of performance and power consumption. I doubt most people would really want to make those compromises.
However, feel free to join the development effort. Maybe you could reach out to the authors of the paper to understand the specifics of how one might implement such countermeasures (the linked article is rather sparse on details) and then you could write some code to do it. In fact, you could work with the team who authored the paper to determine if the methods actually work to avoid the "attack" in the first place.
At the end of the day, any kind of radiation (in its broadest sense) can be used for this, including (body-)heat, cell phones (4g/ 5g) or FM radio, it doesn't even strictly need to originate from within the building, just pass through it to cast a shadow. At least the current generation of wifi hardware (and firmware) is unlikely to grant you any access to obfuscation methods.