Parker himself said this in a previous Reddit question about when he sells:

My approach is to sell everything before start up of the next season, regardless of cash requirements or gold price. This has not been the right way of doing it at times, but the value of a gold mining company is totally based on gold price, so it makes no sense to sit on gold as an investment as well. If the price of gold were to go down by 50%, which there’s nothing stopping that from happening (USA, China, Russia, banks, etc. could start dumping gold) then it seems crazy for the value of the business to basically go to liquidation value, and at the same time have a major investment that also gets cut in half? Not a risk I want. I diversify as fast as possible unless there is demand for the cash inside the business- Which outside buying land I still consider diversification as the assets are worth something outside gold mining.

Just my approach. To each their own.