This is a false conclusion.
On what basis are you concluding the contrary? Neglect to extend reciprocity to cash payers is trivially verifiable. Find in the paper where the contrary is true (that there is a prohibition on cash surcharges). Can’t find it? Yes, indeed it’s not there. Because there is no statutory reciprocity in the statute the article refers to. It is therefore a true conclusion.
Apparently, some merchants have done this in the past, and this is now prohibited. But they can never charge you more than the published price if you pay cash.
You’re confusing cash with electronic payment. There is a new prohibition on surcharges for electronic payment. The same is not true of cash payment. Or do you have a source to cite proving the contrary?
To be clear, proving the absence of law is non-trivial. But if there is a protection for cash payers, I would be very interested in seeing the citation because I will use it in legal actions. I will wait while you dig that up.