I think that's correct. But it is all true at the same time. The cores are stronger because of the higher clock they can achieve and how the turbo clock works,

I think that's correct. But it is all true at the same time. The cores are stronger because of the higher clock they can achieve and how the turbo clock works, and the higher core count does make a big difference. Higher memory speed also helps (though the difference in practice on Z board should be just a matter of what was typically on the market). Intel UHD 630 is even usually a tiny bit faster than the Intel HD 630, even if that's also only from the clock difference - only now with the UHD 730 and 750 did they improve things there.