JBJ 8g Nano Reef AIO Rimless Mod/Baffle question

[DarfrogDojo]

Hello All - today, I "accidentally" decided to modify my JBJ 8 gallon Nano Reef AIO tank. What I mean by that is, while picking up the tank, the hood and rim came off. I really only wanted to work on the sump/baffle area to get better filtration. Now that the top and rim are off, I will leave it rimless, but I still don't understand JBJ's sump waterflow method. The slits in the baffles don't make sense to me. Any help would be greatly appreciated. I posted a video to help explain a little better. Thanks in advance.

 

[Nigel35]

the water falls through the little slits and then to the return pump, back into the tank.