Nothing. Either something follows the scientific method, or it does not. Pre-scientific is a fancy way of saying "we have no evidence for this". Bear in mind, this field is decades old, and has been subjected already to scientific study. All of which have debunked it.

In the typical style of SCAMS (supplemental, complementary, and alternative medicines), this line really just means they're waiting for the one study to validate them in the face of countless studies that have not.

The NLP people have developed a body of models and techniques for rapid and durable psychological changes. This body of work is systematic and repeatable, but the NLP folks haven't (yet!) "done science to it" to try to figure out why these techniques work.