I expect the justification is that everything that CNB is...

I expect the justification is that everything that CNB is drilling at the moment has copper sulfides or oxides so the mineralization is visual, (e.g. you know what to sample), but as others have said, there are limits to estimating % of sulfide minerals in RC chips. Also a lot of licenses and permitting rubbish to go through to let people use XRF instruments, apparently radiation is different in every state jurisdiction in Australia so the radiation you emit and measure in WA is different to QLD, so of course requires different training courses, and state licenses and you have to drag all your field staff away from the field for a few days to do the specialized training course, not really something you want to do in the middle of a drill campaign.

XRF's can be rented (which is expensive) or purchased outright (which is very expensive) if in stock, but nothing gets around the OHS safety stuff so something to look at at the end of the year when the drilling stops for the wet maybe?