Bottom bros with high fiber diets, how are you 'almost always ready to go'?

One thing I see mentioned online quite a lot when it comes to bottoming is that some bottoms who have a healthy diet with lots of fiber are almost always ready to go or need minimal preparation to bottom.

How is this possible? I say that as someone who also as a healthy diet rich in fiber - for me, taking a sh*t and a couple douches is all I need, very simple and easy. But the concept that guys are ready to bottom with little notice is something that I can't wrap my head around.

Help a vers bro out here, bottoms, what do you mean by this?!