Locked door
I don't think there is much more strain on the started motor, as in all large turbine engines I know of, the HP or N2/N3 shaft is turned by the starter motor.
The only extra strain is in the time it takes for the Fan or N1 to stop rotating backwards and start rotating forwards due to the induced airflow before the fuel can be turned on.
On the CF6 the starter had a 5 minute limit and I don't recall ever going past about 1 minute even with the max 40 kts tailwind.