I'm very happy with that line of thinking: it seems obvious that different registers of usage are approriate for different contexts. So "10 items or less" is moving into appropriateness in the context of supermarkets, but not everyone feels it's got there yet: that's fine, I don't agree but I respect the opinion. But I haven't seen any critiques along those sensible lines; it's all been about it being "wrong" in some imaginary absolute sense.