Ben was a brief moment in his recent life, but represented a lot and caused a lot to happen in short order. It's only natural that he's become a larger than life figure in Luke's mind.

"I didn't even know there were other jedi out there aside from Ben." Luke admitted ruefully. "Guess I've got a lot to learn even back home." He thought about it, before adding. "Strange I've never heard Ahsoka's name before now. Guess the Rebel Alliance is bigger than I knew too." After all, it's not like he's been a member for very long. "Well, you know what they say if it looks like a bantha and smells like a bantha, even if you don't call it a bantha it's still a bantha."

Eh, being a Jedi is Complicated, so Luke can't judge. Then again, he doesn't know enough to judge really.