CPU's TDP value rarely corresponds to their actual PPT, though in case on 3990X it's spot on :- ). But that still doesn't say much about cooling.
All 3 (3960/3970/3990) have same power envelope, but difference of 3 vs 4 vs 8 dies under heatspreader. 3990X has twice the surface to transfer heat to cold plate compared to the other two, hence also why it is counter-intuitively the easiest to cool.
But at same time, it's also reason why coolers that don't touch all the dies are poor choice. The ML360 is something of in-between, it has copper plate that does cover the heatspreader on sTR4, but the fins are still only in middle, they cover only the dies on 3960 & 3970X, on 3990X the 4 dies on edges will receive the least cooling.
Still, Noctua UH-14s is much better than ML360 and runs very quiet. There is some unadultered fascination with AIOs in PC world right now and they are all basically trash. Cheap rad, cheap pump, cheap fans. At best they cool slightly better on conventional platforms (AM4/1151,etc..), they are always louder without any exception, and sometimes they just fail (Enermax).
The person who adviced you this build had only paper knowledge. I already run 3990X on U14S, with temperature in 60s.
Lastly, right now, Zenith II Extreme & II Extreme Alpha, cost almost the same, but you get better board (plus a PCI-e add-on card for SSDs). Get Alpha, it's either the same money or 50-100 euro difference depending on shop.
I can guarantee you there will be better support for Alpha in long-run too... Asus very quickly forgets about support.