There is nothing wrong with the USB15 header as Thercon Jair correctly stated. That header is a single port. You can get a hub or a splitter to connect to USB1112. Many have had success using the NZXT hub and it is inexpensive @ $20. You could also use a commander Pro but @$70 it may be a bit overkill just to get two internal headers from one. Another inexpensive option is a USB splitter like this <
https://www.amazon.com/gp/product/B06XD3WZ77/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 > @ 10.00 on amazon and you can find them elsewhere just search for USB internal 9pin splitter 1 to 2 male.
Or if you are cool with it leave the AIO in USB1112 and connect the front USB 2.0 i/o to USB15 and just know that one of your front 2.0 sockets wont work. I imagine you would need two front USB 2.0 simultaneously on very few occasions.
Other systems in addition to rig in the profile specs:
Aorus Master x570, 3950X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, Sabrent 1TB, 860Evo 1TB, 2080 Super, HX1200i, Celsius S36, Define S2, pg348q
Aorus Master x570, 3900X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, 860Evo 1TB, 5700XT, HX1000i, H150i Pro, Obsidian 500D, LG32GK650F-B
MEG x570 Unify, 3800X, 32GB GSkill c16 @3800, Sabrent PCIe4 1TB, 860Evo 1TB, GTX1080Ti, SSR-850PD, Celsius S36, Define R6, u3415w