I used to climb a lot, and we'd climb in a climbing gym on weeknights. No chance at having enough time to get on a crag for a goodly portion of the year.
So I get that the experiences aren't always transferable. What weirds me out are the differences that seem at odds with each other.
Like
delbiker1 , I get much more saddle pain inside. I wonder about that. I know that part of it is software that punishes you for taking a momentary coast (which is stupid, but not talking about software here). It means that my IRL habit of taking a moment to adjust, let the blood flow ... doesn't happen. And I definitely don't feel 'right' coming out of the saddle. Just feels unbalanced, like I'm way too far forward.
Does it help with overall fitness, and thus help my outdoor cycling? Of course. But so would any fitness-oriented activity. I actually feel like I'm picking up weird habits, both physical and psychological. It's far more tempting to push yourself to a limit inside if you know you don't have to grind 12 miles back to the car after a tough interval. I guess that's good?