At this point, yes. I think the Clark style zapper has too few frequencies for them to sneak in test frequencies. And they're trying a variety--and tracking more than one or two sets of trials would be more difficult. While people are paying for their zappers *ack*--I'm sure it's nowhere near the cost incurred by the testing/surveying/tracking folks//paperwork. So more than 2 seems unlikely, especially as limited as clark zappers are, in frequencies.
Frequency is what they're gathering info on now--which ones are most effective. So you need one with lots of frequencies to hide it amid. I think they're got the voltage as high as it can go, but I'm sure they're pushing for more if possible.
Once they get that, the FDA will probably go after the other clark style makers. Get one now, before the get their tests done, would be my advice, or try and figure out how to make a choke coil of some sort as Dr. Clarks says.