I first thought cool. On second look I see it is based on PHP. I'm sure newest PHP is really fast and advanced but I don't want to invest any of my time on that language (just my personal opinion).
Update: OK, it also runs on nginx. Made a wrong claim it does not run on it. Sorry.
Well that shouldn't be true. Firstly there is no good reason why any PHP framework would ever require a specific web server, so the claim seems dubious. A little reading in their installation guide confirms Grav should work with any web server: https://learn.getgrav.org/basics/installation