I disagree. If building an ITX system really no point in an X board anyway. Current 400 series of B boards are just as good as X series on ITX platform and the chiset offers no tangible benefits.
What is an ITX system builder getting for buying a 500 series motherboard:
1) 570 chipset with active cooling.
2) PCIE 4. Is this really needed? PCIE 3 is fine for NVME drive times. A 2080 Ti only just comes close to saturating PCIE 3 bandwidth at 8x so if running at 16x loads of room for future GPU upgrades.
3) Better VRMs. Deffinately a positive but only if buying a 12 or 16 core part. VMs on current 400 series ITX boards will handle overclocking an 8 core part just fine.
4) Faster RAM speed. The returns are diminishing at the cost of latency. Not much performance difference for games running 3200 vs 3600 with current 2000 series CPUs.
Edit: way off OP question. Sorry.