Funny how Gaban was supposed to be testing Luffy and Oda shoehorned Zoro in there as well for absolutely no reason.
People really gotta stop betting against Zoro, it makes almost as little sense as betting against Luffy. Oda hypes him every chance he gets.
Gaban just wanted to know if Luffy could handle whatever's about to threaten Wano and ended up satisfied with both Luffy and Zoro's strength, so stopped immediately once he got his answer. It was a test and they both passed, now Gaban's gonna fuck off and let them deal with it.
Hopefully we'll see more of Gaban's strength, the best hype he got this chapter is that both Luffy and Zoro wanted to keep fighting him - they're only interested in strong people.