Your case is addressed in this sentence from the post you quoted.
This does not mean that DP to 2 HDMI will not work, just that NVIDIA has not directly validated it.
From the thread I linked, another user has a working solution for your case Support on mst board - #6 by jameskuo
Hi WayneWWW:
Sorry for the late response. We are using Synaptics vmm5320.
We are trying to use DP → DP + HDMI or DP → HDMI + HDMI. DP → 2 HDMI works fine.