Building a Nicoll-Dyson laser is quite possible, if one has the necessary technology level.

James doesn't have to describe that. He only has to describe the laser, and some applications for it.

The fact that, due to matters of scale, it's not possible right now, or for the foreseeable future, is not likely to matter to the USPTO, which typically has a grant-first-ask-questions-only-during-lawsuits policy.