They had a good system but they didn't follow it. Dual core CPUs with hyper threading showed up as i3, i5, and i7. Then an i3 showed up with six cores in the 2018 mini. Logically it should have been i7, four cores with hyper threading; i5, four cores no hyper threading; i3 two cores with hyper threading; Pentium, two cores no hyper threading; Celeron one core with hyper threading; Atom, one core no hyper threading.
They you could go up the same way so i9 would be six cores without hyper threading the all the double digits could have hyper threading so I-value just becomes core count.
But logic and Marketing have never gotten along.