"Extra" content limit on maps and what counts

I never knew about that before, but there are claims that maps have a maximum amount of "extra content".
So what exactly counts toward it? For example, does "core content" (beasts, betrayal, delve and incursions) count? If so i would absolutely avoid specking into beasts, because "extra" content (that can be blocked) is X100 more worth than some extra beasts, but my main questions is - harbingers and beyond demons (and stronboxes(lol???)) counts as well? If so, I would not spec them EVER, I always thought there were more some extra risk/some extra reward, but if the take extra content "slot" then absolutely NO

So anyone can 100% confirm?

Have you checked this ?https://www.poewiki.net/wiki/Extra_Content
I doubt it's 100%. Perhaps even as low as 99% but that's essentially how people play the game.

If there really is a limit to how much additional content can be added to maps, it could really change how we approach mapping strategies. Instead of just adding more beasts or omens to ramp up the difficulty, you could focus on optimizing the elements that actually matter for success. It’s an interesting balance between content quantity and what truly makes an impact in the game. Has anyone tried testing this out experimentally or figured out how much can be added before you start losing effectiveness?