That may well be but it's not 4K unless you stretch it out over the entire field of view which would be crazy huge :) at a normal size it would be about 1080p effectively, maybe a little higher.
That's great, but it's absolutely not high DPI. iFixit estimates the pixels per degree (ppd) of the AVP at ~34 [0]. A MacBook Pro at 20" is over 90 ppd [1]. A 27" 1920x1080 display at 22" would match the AVP at 34ppd.
See also this post which has more numbers: https://news.ycombinator.com/item?id=39323574