[CustomRCmodels]

Nothing wrong with it
That’s how these GRU’s are mounted : long enough screws to bolt motor and GRU to the transmission . Otherwise you would have to disassemble the GRU to mount the motor .
And the included pinion-gear goes on the motor-shaft , since upon depending which type you have here ( 2:1 , 3:1 , 4:1 ) the pinions are different sizes .
( I am assuming the pinion-gear you are showing in the photo came with that GRU )
And that the setscrew sticks out doesn’t matter , since that gear which this pinion runs against it is a very thin gear , means you have to do this very precise ( adjustment of the pinion gear on the motor shaft )