Now I'm not entirely certain, but I think you're reading that wrong. I believe they're trying to say that on most models, the display is laminated to sapphire, implying that the Sport model is laminated to the ion-glass instead.
I am not convinced either... If it were true then they would just say that for all models and they specifically don't say that for the sport models. They say " On watches in the Sport collection, protection is provided by strengthened Ion-X glass."
I think I might be reading too much into it but apart from the materials, this could be a key differentiator for the higher price of SS model as screen lamination adds some cost.
This might not be apparent at first look....but i can definitely see the difference between my wife's iPhone 5c and my 5s. The lamination would make for a bigger difference in readability on a much smaller screen. I hope some reviewers point this out ....if at all there is this issue.
It would create a production headache to make one model with laminated glass and one without all in the same chassis. Laminating the glass allows for a thinner body, the component arrangement would have to be very different on the sport and SS for this to really work. I think it's just a clumsy sentence.