At lot of replies to that Verge article seem to be addressing the click-bait title and not the content. The content is concerned with why an old Macbook (with comparable specs to a new iPhone) will handle the web much better than said iPhone.
I need to do more specific digging on this to have a good answer. From the bits I know, mobile browsers offer more conservative support for caching & hardware acceleration. Phones are way more sensitive to battery use & heat than a plugged-in laptop. You can't really directly compare a phone to a laptop, even if they seem to have similar hardware numbers. The form factor & use cases matter.