FWIW, I think it is pretty common in the US to use “pristine” to mean, “really, really, really clean”, without regard to why something is clean or which sense of “clean” is meant. So a pure, untainted tract of wilderness is pristine because it has been left untouched by human civilization, but a mopped and handscrubbed tile floor that sparkles with cleany-goodness is also said to be “pristine”. It isn’t much of a stretch from pristine (well-scrubbed) floor to pristine (heavily-proofread) text. So I found the reference to “pristine” propf to be unremarkable. But I agree that another descriptor would have been a better choice.
Edit: I should clarify that by “heavily proofread” I mean that several errors have been caught and fixed, not that the text is covered with proofreader’s comments and corrections. I’m assuming that by pristine the speaker meant both that it is a new draft of the text which does not contain any comments or marks AND that the text has had either all or the vast majority of any typos or other errors fixed (I.e., it has been scrubbed of such errors). If the speaker just meant that it was a new draft with no proofreader comments or marks on it then it was an even worse word choice than I thought it was.