i'm looking to find out the correct procedure for when start valve will not close after main engine start on airbus or boeing aircraft.
I would say that the procedure provided by your company
is the correct one.
As has been mentioned there is a real risk of starter overspeed, especially if de-clutch speed is reached before the bleeds are isolated.
I'm not sure that continuing an engine run with a starter that might have popped its lid is such a good idea.
Also, if you look in the QRH for your particular airplane, I'm sure that the drill is similar to the one your run-up guide.