I've edited the text slightly. Sorry to confuse you. Actually the confusion is caused by your collegues. There is no reason to do what they are doing, unless it is SOP's although I can't see why!
When you go from 'OFF' to 'ON' the door will show open after a few seconds, you can then select 'START' anytime you like, 1 min or 1 hr later doesn't matter and the starter will engage and ign/fuel etc will come on and hopefully it'll start.
If you go from 'OFF' through 'ON' to 'START' the door has to open first before anything else happens, as soon as the APUC sees the door open it will then start the starter and fuel/ign etc.
I was doing this on an A/C a few days ago as there was a problem with the APU, I was calling up the EICAS maintenance page to see what was happening, I went from OFF to ON and after the door showed OPEN then went to START (the START position is momentary and the switch will (should) always return to ON) this was only because I was trouble shooting a fault, normally I would go from OFF, then to ON, then through to START and then back to ON.
Hope that helps and has not confused you more.