Yeah, I'm not sure. I opened multiple tabs of this website right next to each other (tried a couple other websites as well) and they never stacked. Sometimes I keep several threads open in tabs from this forum over long periods of time. This is so I don't have to keep clicking the links in email notifications of threads I'm subscribed to. All of the tabs will sometimes literally take a full screen of room or a couple rows and it is almost stressful to see all that. Having a single stack of them would be great.
Oh and question, do some websites not stack for some reason? Or should all stack as long as there are multiple tabs of the same website adjacent to each other? And, if it was all the same site but just different pages on the site, should they stack? Does this site usually stack for you?
I plan on restoring my iPad and iPhone as new (at the same time) in the somewhat near future just to rid them all of junk apps and such that accumulate. Maybe a fresh install will fix this issue.