iPhone 8 on iPhone 6 analytics

Solution 1:

The 'brand/marketing name' & the model designation number don't ever match.

The iPhone 6S's model designation is 8,1 [regular 6S] or 8,2 [6S Plus]

You can see a list of all models, including marketing names & model designations at Everymac's iPhone Specs page

They actually went out of sync with the second ever iPhone released. It was called the 3G, even though it was only the 'version 2' & carried the designation 2,1, because of its new 3G phone capability, rather than the previous GSM. After that came the iPhone 4… even though it was the 3rd gen not 4th, & they've been out of sync ever since.
They did briefly re-sync for the iPhone X, but the next year's XS threw that out again.