While it ensures pin point stars, it also mandates the use of higher ISOs than, for example, the 500 rule.
I usually try to stay beneath ISO 3200, if possible. Otherwise the noise in the photo will become too noticeable. And this is also the problem with the NPF rule. While it ensures pin point stars, it also mandates the use of higher ISOs than, for example, the 500 rule. The truth often lies somewhere between the two.