I think there are a few more differences between different variable frequency drive (VFD) designs. For example: I've used VFDs that never use output load reactors, and can go, depending on the VFD model, 300 to 1000 Ft between the VFD and motor unaided. To exceed that distance, they use an RFI filter. Not tooting a horn, but pointing out one of the manufacturer's capabilities versus others, with respect to wanting to define the application as thoroughly as possible before taking on system design aspects. No VFD brands mentioned, but there is a fairly broad spectrum between manufacturers, some having capabilities that can render some better applicable than others with cost and other incentives considered. When these situations present themselves is when at least some of the questions are asked, and for me at least it's an effort expended to find which manufacturer can supply the best VFD for the application.
Different VFD manufacturers have different limitations and or requirements for distances, thus the generic approach of "X feet" as to not be manufacturer specific. Sometimes I find pursuit is outweighed by the sense and convenience of recommending another company better acquainted with the application as the course to take. I don't shy from doing that, especially when whatever it is looks to be outside my realm of experience. For me, if it isn't in my niche and I know of another outfit better acquainted with what needs to be done, I'm more than happy to refer an inquisitor to them and have them take it from there. I see it as going for aspirin instead of a headache! LOL!. BTW: I think most training classes not needing to cut too deep into VFD theory is excellent and as well put as it can get. I've been to a few, as I'm sure you have that did just that without it being necessary, and have seen class attendees (along with myself) drift off in boredom.