Well, I guess if you beleive what Chevron is saying on that web page then, only the 5W20/5W30 are formulated with Iso-Syn technology. So, I would say that the 10W30/10W40 are not!
Have you checked other sites?
Did the 10W30/10W40 use to have Iso-Syn?
When I did buy Chevron oils (5W30), I would often see bottles on the shelf both with and without the Iso-Syn wording on the bottles. I'd grab the bottles that did say Iso-Syn just for my own comfort. Not that the bottles without the Iso-Syn labeling was a lesser quality oil, IDK!
Also, this isn't to say that I won't again buy Chevron oils, it just means that I haven't seen any lately or at the price that I want to pay. Last time I bought Chevron oil, I paid qt.