The most meaningful difference I can come up with is that "taking off/losing shirt" is more likely to be played for fanservice or showing a character going through a rough time, while "default shirtless" is more likely to be played for power fantasy manliness. That's just a vague hunch on my part though, I don't know if that's actually the case. And of course, these purposes can overlap.
We also already have Shirtless Scene. I guess I can see the difference between "scene without a shirt" and "this character loses his shirt a lot", but I don't think it's a particularly important difference. Just mention that the character gets a lot of Shirtless Scenes and call it a day.
And of course both remain distinct from "never wears a shirt to the point that it's a noted exception when he does."
Writing a post-post apocalypse LitRPG on RR. Also fanfic stuff.Besides, Shirtless Scene is just the one moment characters take off their shirt, just to have a fan service-y scene. Walking Shirtless Scene is about the character themselves and how they're used and portrayed. A character who removes their shirt multiple times is more apt for WSS than SS.
Working on: Author Appeal | Sandbox | Troper WallReally, I'd want to change that laconic anyway. Focused too much on being "witty" rather than clear.
How about "A character who never seems to wear a shirt." Or, if we want to include the expanded definition (I'd prefer not to because I prefer laconics to stick to the basic trope, but anyway...) "A character who never seems to wear a shirt, or always manages to lose their shirt."
Writing a post-post apocalypse LitRPG on RR. Also fanfic stuff.Or, "A character who is often or always shirtless".
Working on: Author Appeal | Sandbox | Troper Wall
Crown Description:
What would be the best way to fix the page?

I don't see why it should be split; it's a concept so similar in execution and meaning that I just can't see it as a different trope.
Working on: Author Appeal | Sandbox | Troper Wall