yes, em sensitivity needs a lot more research IMO. I was very careful when designing the waveforms for ICES-PEMF to not include any energy in the frequencies that seem to cause a lot of em hypersensitivity (radio frequencies MHz to GHz generally).
I would go further to say that there are at least several or maybe many different types and biological mechanisms of em sensitivity. For example, you could be sensitive to too much intensity or duration of biologically-beneficial PEMF, and different people would have different levels of sensitivity, or you could be hypersensitive to radio-frequency signals (totally different from ICES-PEMF, this would be MHZ to GHZ frequency sinusoids), again at different thresholds and maybe different frequency ranges for different people. This latter would almost certainly be an entirely different biological mechanism of sensitivity.