One additional reason for launching plugs in an aluminum head (in addition to too few threads) is that aluminum has a much greater expansion rate than steel. EVERY time that head is heated up to operating temperature, the hole expands and loses some grip on that less expanding steel plug. I realize that is oversimplification to the max, since there are TENS OF MILLIONS of aluminum heads in the world on all makes of cars that NEVER launch a plug, but valid, none-the-less. I think the ones least likely to ever have a problem are the ones that use a very long thread pattern, both in the head and on the plug. I don't think it would require a rocket scientist to tell Ford that they had greatly increased the chance of blow-out problems by putting a 4 thread hole in an aluminum head. You could likely get away with it in steel (and even then they usually put more than that), but not aluminum for the aforementioned reasons.

The aforementioned 14 lbs of torque with the 4 threads was an IQ test, and they definitely failed it!