A couple of right angles not really make it light tight either.
I remember going caving and we would have to go 100m or more through many different turns before we all turned our lamps off and truly experienced perfect dark.
The last time I used a daylight tank was in the mid '90s so maybe newer models are different, but I believe they are made out of black/dark plastic? Several right angle turns of black plastic provides multiple opportunities for a visible-light photon to be absorbed into a black body where it should be re-radiated as infrared (heat).
A hole/leak in the metal wall of a Faraday cage is going to be a lot more reflective and can easily act like a crude waveguide[1].