My response is that that image is outdated. I know other people who used the R4 GOLD Pro succesfully and I also talked to one of the devs behind the ntrboot flasher and he said that it was tested succesfully.
This is a more updated picture taken from the Nintendo Homebrew Server, from 27/01/2018:
and look, R4 Gold PRO is now in the "Compatible" area, along with all other =>2014 r4isdhc.com models. And they also put "cheapest" next to them