Almost the same thing happens to NSK around my area...
I used to pay using PayWave (not SPay) before for small purchases.. no problem..
Later, I started paying using SPay... Altho got some hiccup in the beginning.. later no problem...
A few weeks later, when I want to pay using SPay, the cashier (new, I think) donno how to process..
She asked the higher up... and she said "No, we don't accept payment using PayWave... only physical (and PIN) are accepted"...
She also asked me who did authorized my SPay/PayWave payment before (I did it few times already)...
And I saw her later talked to all the cashiers to not accept PayWave anymore...

Using PayWave and SPay Wave are different as you'll notice that the card number shown on the receipt is not exactly same.
As I said earlier, it's better to just say use Wave instead of SPay. Let them figure out themselves.