While you are right there is always possibility of contamination...

While you are right there is always possibility of contamination at multiple stages from drill bit to sample bag, any decent experienced senior geologist can spot potential problems and deal with them in real time. Ie. keeping the cyclone clean after every rod is complete, be it with an air hose or if water is intersected physically getting the offsiders to completely clean out the cyclone and splitter, air lifting and blowing the hole clean if clays and/or water is intersecting for as long as is needed, and keeping the driller checked if he starts to drill to fast. The odds of that intersection being from smearing and/or contamination are so low (like seriously less then 1%) if the above is done.
From what I can gather, the MD wade has been on the rig during this campaign. According to mates at Goldfields he is a pretty passionate and switched on geologist, so I feel pretty comfortable he knows what he is doing.