I was brain storming on the subject, and I'm certainly not in possession of a serious comprehension of it, only interested. Besides earthing myself, w no undue effects, Ive studied about it mainly thru Dr Tennant's work.
Your points are interesting tho suspect in some way still to me.
Frequency may play a role of importance, tho that would rarely be negative at the low freqs found emanating from grounded utiity poles. And since the electron field is the same whether a/c or d/c, that shouldn't be an item either, not withstanding, or in disagreement with the concept that the returned (stray) ground field voltage retuned from utility poles to utility plants from only about a mile or so radius, is negative in some way, (rated at about 15% cost benefit reported by S Millham. and btw the earth does have a lot more resistance than a metallic wire, so---hmm not sure why he mentions that on his site).
If he is not referencing voltage actually (since its all the same and good for us unless it's too high, maybe he is really trying to emphasize frequency, tho in that complaint, the return frequency mentioned is low, 60 to 200 hz here, not of the higher types, which interface our systems whether we interface the earth or not.
Unless we are in an area with another ground based or directed source of unusual high or ultra high frequencies (HARP?) the caveat seems confusing or in error. We all know we are living in a world wide atmosphere of frequency forms that impinge upon us. Pretty inescapable when we consider the dimensions and numbers involved, furthermore aside from the size differential in each particularly differentiated vibrating field upon the general field (earth ect), each would mainly be affecting us on the resonant level(harmonic) that is existent in us. (tho with such a new and open topic ideas abound, tho proof is minimal still) And since again this is irrelevant to the Voltage Field associated electrons found associated w the earth field, but easily accessed via earthing, no matter the other frequencies or voltages found surrounding or therein. I still cant see the discrepancy in my post based on the work of body voltage experts like Dr Tennant.
I think the post still has veracity as a consideration to the negative experiences related, especially since most all our experiences and complaints of this sort are so subjective.