To cause cancer radiation has to have small enough waves to invade cells and damage DNA. Cell phones and routers do not have small enough waves no matter the anecdotal evidence.
That may be true, however it does not explain the results of the seed germination in the experiment. This assumes the test of science of course: that it is testable, verifiable, repeatable and falsifiable. If it meets these criteria then these larger wavelengths do have at least some effect on living organisms, even if plants are not human beings.