Well, between TL having 50% higher base+boost clocks, ~20% higher IPC and most software not scaling anywhere near linearly to eight cores, it does not seem that far-fetched that a fast quad could be signfiicantly faster than a much lower-clocked octo in a fair number of cases.
TL doesn't have higher IPC at all.
Its the same as Sunny Cove... their performance enhancements come from much higher base and boost clocks because its a 4c/8th part (giving more room for higher clocks and of course more GPU cores).
Its funny how Intel conveniently forgot to mention that... or most reviewers who came out with similar titles of 'Intel could give AMD a headache'.
At any rate, Zen 3 APU's will be coming out next year, so that will actually close the single threaded performance gap (if there is one at same TDP). The only thing Intel may retain a real advantage is in iGP since enhanced Vega in Zen 3 will remain as is... however, as Zen 3 is a much stronger CPU (performance-wise) compared to Zen 2 and an entirely new uArch to boot, there's a good chance games could easily benefit from this and result in increased performance as well (so the IGP may still turn out to be the same or slightly behind XE).
Although, Intel still cannot make an 8c/16th low power CPU apparently, which makes their multi-core performance sub-par.