Hey this is probably one of my favorite examples of this trope thank you so much.
Bruce Wayne meets Clark Kent at the end of a gala, when Clark lands after having to make an emergency rescue.
Cue Bruce running up to Clark(Superman[his best friend]), staring him down, and then stating very clearing that 'this makes so much more sense. what a relief. You probably know who i am then.'
and ah, yeah, reporter clark kent is slightly familiar with bruce wayne, by reputation at least.
And now he suddenly has bruce popping up in his life, along with his child, seemingly certain that they're best friends??? and there's no sign of the brucie he's familiar with from the tabloids, instead there's this very intense serious man who keeps bringing him random inventions to help, including surgical equipment laced with kryptonite in case he needs stitches? How is he going to explain this to batman.
Meanwhile Batman is the most at ease he's been in forever, of course superman is just like that if he was raised by the kent's. and of course superman would've already known his identity even if he's too polite to bring it up.