When I buy something BNIB costing hundreds/thousands of $$$ & pay the price for it, I expect that it is BNIB, "unmolested", unused for testing, demo & whatever other crap reasons, period. If a shop's practice, for the sake of sales, is to allow people to try/test things out, or to use them for demo, there should be separate sets like demo/display sets which are subsequently sold at a discounted price & stated as such. The shop should bear this costs & not the buyer, especially if the shop is known to sell at higher or premium prices.
Imagine if demo or display sets are sold off to you as BNIB, wont you be upset? So we should not make excuses for it as it only encourage & embolden them to misrepresent to or mislead their customers, to dishonestly palm off used items, regardless of the extent of usage, as new, relying on buyer's lack of knowledgable about such matters like checking shutter counts. Now I know which shop to avoid. I believe no one would suggest that hey there's really no such thing as mint, unused cameras/lens since these would have already been "used" by the production operators, "pre-owned" by the shops(owners) already & as such all this do not matter
Of course TS could be mistaken about the shutter count/actuations vs file number sequence & should clarify it here since he validly raised this issue.