Well he said it about Radradra. If he wasn't talking colloquially about finishing near the back of the group then he ran dead last. Either way the point stands. Fullbacks need to be very fit (like Gutherson) and not just fast, strong and skilful (like Hayne and Radradra). Here's what Arthur said about it:
“He (French) knows there is an opportunity to start the season at fullback and one of the demands of it is that he needs to be able to run a lot and get a lot of kilometres into your legs and not miss any opportunities.”
https://www.parraeels.com.au/news/2018/01/18/arthur-discusses-depth-and-round-one-selections/
What the media thinks is irrelevant. What is very important, however, is how Hayne compares to the other fullback options in the team. Gutherson might be our first choice fullback, and if he is it's because he is the fittest option. Hayne and French both leave him for dead when it comes to speed. Hayne is also stronger and has more skill. I reckon French has shown more with the ball as well. But Gutherson is the type of fullback who is always there in attack. That is a massive benefit to our forwards and halves.