I can see your point although you totally ignore his comments about price being a limiting factor on the amount of VRAM, however of the games listed at 4K Ultra
Shadow of the Tomb Raider uses 7780MB &
Assasins Creed Odyssey uses 7424MB so significantly outside of the quoted 4-6GB, the rest use 5-6 GB but they are all cherry picked examples. I am currently playing Horizon Zero Dawn at 1440P and Memory useage on my 1070 is generally running well over 7GB even with reduced settings, and my next 'game' will be MS Flight SIM which
at 4K can exceed 10GB. I've no doubt that 10GB is probably enough for 99% of current titles at 4K but it's reaching the limit and for people like me who can only invest in a graphics card every other generation I don't think 10GB will be enough in 2-3 years time for 'next gen' titles. It's within NVidia's remit to pursuade people otherwise which is why it's best to take their statements with a good pinch of salt, but personally I won't be buying a 10GB card, rather I'll wait to see what AMD bring to the table and potentially what the pricing the 3070 & 3080 super / ti varients with more VRAM release at.