"What's the point of a recent OPC"
Know the area, not the customer or operator. Short-term contract, so looking for mercenary international pilots (as opposed to your nanny state, cradle to grave, hotel must have a manicurist).
My guess is that an LPC + recent OPC would suggest a pilot that needs a minimum amount of training to meet standard. Or taking the Australian approach, test to standard and then add training only as required (only slightly /s).
Pretty standard consideration for short term, also weeds out the non-current in case the customer is one of those "50 hours initial if expired two years".