He recognizes that Nacho and Arturo had their own plan, and certainly he had to nip that plan in the bud.
There’s also a lot of information that Gus can get from Nacho as we play out the season, because he’s been one of the closest people to Hector Salamanca, and knows how the operation works.
He recognizes the way the operation has been working has not been completely as fruitful as it could be.
So I think it was really appropriate for him to bag Arturo in front of Nacho.