When the crank is at TDC for #1 (you must check the cam to confirm it is on #1 and not on #4) then with the lock pin in place in the pump sprocket/bracket, then the belt will be on the correct tooth when installed. You still need to dial in the fine timing using a dial indicator or pulse adapter and strobe.
The key/keyway do point to around 10 o'clock. That doesn't matter so much though. It does matter when you get the pulley on and start lining up timing marks. Lining up the shaft keyway at 10 o'clock does sort of give you a head start in having the pulley close to where it needs to be I guess. If the whole thing weren't designed by Germans I can't help but think the keyway might be lined up with the pulley's timing mark.