@tracer bullet : Again, the answer lies within my OP, wherein I stated:
Personally, I've made beer recipes that were CaCl2 forward, and then brewed essentially the same recipes in CaSO4 forward water and not truly noticed any difference.
And it seems that in a majority of their test cases, when Brulosophy has touched upon this subject (albeit willy-nilly) their blind to the changes audience of testers have generally concluded likewise. Where I perhaps erred in saying this as early on as I did was in not being more clear as to maintaining a requisite Ca++ mEq's level consistency.
I then moved immediately into looking at Cations as opposed to Anions with respect to where flavor differences may lie. And then I offered a link to a peer reviewed scientific study which has discerned that the very sense of taste itself revolves entirely around Calcium, which is a Cation.
And then I detailed as to why (in a world where some mash and sparge, and others mash only) the ppm's of Calcium alone are not sufficient (and rather are highly defective) in defining what is required for Calcium, whereas mEq's are fully sufficient.
As to calculators, one would hope that they internally convert ppm's into mEq's, and more importantly, do so correctly, whereby to deduce downstream solutions more correctly (which is another subject of contention in itself). But the point of educating is to provide the tools which will permit people to derive usable answers without the crutch of a calculator. In a world of complete dependence upon smart phones, this may seem highly confusing. But I've gone better than 25 years now without even owning a TV, let alone a smart phone.
As to why calculators call for input in ppm's (mg/L's), if (as
@dmtaylor has succinctly deduced) virtually no one at this stage of the game at the home brewing level even knows what an mEq is, there is little choice but to digress to ppm's. Hopefully at some future juncture this will change.