Gas Bags, I'm not sure of the intent of your reply re dumbing down, but if you doubt that there is a procedure to strap the fan and do a core EGR, then go and find a P&W JT9 manual and it is detailed in there. Like I said, I've done it a couple of times.
The other time I have strapped the fan was for a 3 engine ferry, however this depends on type as I've done another 3 engine ferry on an A340 and it was not required because flight time was below X (?) hours and engine was allowed to windmill as there was no damage to the oil system. Was a bit weird raising a DD along the lines of Engine No1 inop - not to be used.
So to answer your question, this is what fan straps are for.
As for the original question - I've had a look in A330 Chp10 Parking and Mooring and I can find nothing specific as to securing the fan when parked, but only to fit intake / exhaust covers if parking for up to 15 days or more. Basically I would say (for the types I have access to), windmilling on the ground is ok. This is based on the pretty basic checks required after an IFSD dependent on failure reason, e.g. even after a IFSD allowing windmilling for over 30 mins you basically just need to check EMCD and oil level before running the engine and rechecking the EMCD. So if an engine can windmill in flight for a considerable amount of time with pretty basic checks (post fault rectification), then windmilling on the ground at lower rotational speeds should not cause a problem.
Other aircraft /engine types will more than likely have different criteria of course. Maybe B737 NG's have some tighter criteria as they are the only ones I can specifically remember seeing fans secured whilst parked on the ramp.