Looks like the Matrix Platinum uses a separate heatsink for the VRMs: http://www.hardocp.com/image.html?image=MTM4NzEyODczNWV2ME9YQmxoVUNfMV8yOF9sLmpwZw== the 'durability frame' it doesn't seem to be part of the main cooler assembly so the G10s' fan should keep the temperatures within reason.
A few pointers on the G10, though:
It's quite hard to assemble, especially on AMD cards, holding a AIO pump/coldplate against the G10 while sliding it down the 4 tiny mounting screws is tricky.
On my R9 290, those 4 little screws pass through the inner holes in the G10, check they'll pass through easily and are exactly aligned, you may need to gently bend one or more screws to make the G10 slide easily over those screws.
The mounting nuts DO have a crosshead, use a magnetic screwdriver to make life easier.
With no springs or standoffs to precisely clamp the pump/coldplate to the GPU it's easy to get uneven hold down force, which can result in wildly over the top temperatures, I messed it up during one install and got 95+C load in seconds! Don't panic, just shut down and reseat the pump/coldplate.
Way that seems to work: Get all 4 nuts started then, while holding the bracket/pump/coldplate down, run all 4 nuts down until they just make contact then tighten them down 1/2 turn at a time, about 1 and on half turns.