Yes, it's semantics because a "hero" in that setting isn't supposed to be a literal hero, it's just a fucking profession that involves saving people.
They are a specialized and glorified mix of police officer and rescue worker. There is no need for them to be completely selfless or heroic and doing it for the sake of money or fame is perfectly fine as long as they get the job done.
If they were called "Super-helpers" or some dumb shit like that Stain would literally have nothing to complain about so yeah, semantics.
And, again, even massive attention whores like Best Jeanist and Mount Lady or assholes like Endeavor have shown that they can be as heroic as All Might when they have to so Stain would be wrong even without the semantics issue.