I have seen this done a couple times that I can think of. It was done with a piece of wire way rather than a box though, to route wires out of one box and into another.
Why this made more sense than just running a piece of conduit between the two boxes is something else.
Maybe they just used what was laying around.
it's a pain in the butt to pull with large feeders....
only once in a refinery, did it work out... it was a 4'x4'x1' deep box with parallell 4",
and we used a large wheel, drilled a hole in the back of the box the size of the axle,
and made a straight leg of two pieces of strut, and put the wheel inside the box...
pulled it right around, with a lot of soap.
usually it's a hypress and tape deal. fixure 8'ing a bunch of cable and having the length
come out right at the end isn't much fun.