I'll give you the Mario Golf comparison, but I will also maintain that it's ridiculously out of character for Rosalina ("god fainted because she missed in golf"), and I think her bogey animation should have been completely different (depicting her as nonchalant/aloof to it would have been much more in character. Or having her accidentally hit a ball into orbit, would have been a nice gag with the space theme). I'm not too bothered by it though because IIRC, it's basically a bit of an inside joke for the bogey animations to be stupidly over the top and out of character in Mario Golf (like Mario sobbing uncontrollably), so it's just a series tradition thing. Also Rosalina's portrayal in that game is otherwise quite fantastic.
On the whole though, I just feel Rosalina has more meaningful elements of being a tomboy. And no, you really don't have to read between the lines. That MK8 render speaks for itself (and CPU Rosalina's often default to that set up in game). The Garage is literally right there on the Observatory and she points it out to you. And most people do read the first chapter of the storybook at least, as the game sort of leads you into the library when it first becomes available, so most people check it out thinking there might be more levels in there. And since the part where Rosalina fixes Luma's ship is in the first chapter, it's right there for a lot of players. And then her 3D World voice clips are there constantly as you play as her.
The common misconception about tomboys is that they have to be a girl that acts like a boy all of the time or JUST like's boyish things. But that's not the case. It just has to be at least a noticable part of their character, and I feel it is with Rosalina most of the time, but I don't see it with Daisy most of the time.