Yup I have seen the PT-6 start with the throttle at idle and, yes, it works because of the flow divider , but why do it? You could do the same thing with the T53 on the 205.
Trying it on a 250 and you are buying a new hot section…you will never be fast enough to close the throttle before the needle pegs. More than one 250 has been “Boat Anchored” due to the pilot not checking the throttle position of carrying out the throttle check incorrectly.
One fellow returned from lunch and found the throttle in the full open position, someone had entered the cockpit and fooled around. Fortunately we had a policy of turning the fuel valve OFF, pulling the ignitor CB and then.disconnecting the battery before leaving the aircraft unattended.
Some folks get confused between a cooling run to lower residual temp before a start with ignitors on and a drying run to blow residual fuel out of the engine if the darned thing didn’t light off on the first attempt. ( Happened from time to time with a cold soaked engine and Jet-A ) in which case the ignition CB would be pulled to avoid loud noises startling the engineer. I miss good old Jet-B.