And that's why a request for a waiver isn't just a formality, dispensed with in a few minutes. The FCC needs to determine that there isn't a risk to the public or to other established users of the frequencies in the specific case requested by the requestor. Lots of waiver requests are for experimental uses (the Amateur Radio community does so from time to time), but those typically designate small groups of stations and locations. As this is a portable commercial product, I suspect it was a lot harder to decide on.

TFA says "the circuitry combines the echoes at different frequencies", but I suspect "circuitry" is a layman's term and that this is truly done in software. Various DSP chips would be excellent platforms with which to do so. If so, then the starting point is a "RADAR camera", which gets turned into a motion detector through image processing. In which case those plants will be quite visible, along with anything else that has edges. The stolen Van Gogh on the wall, however, will be indistinguishable from Dogs Playing Poker.