The purpose of that drilling was to determine overall reserves of spodumene, within the target general exploration zone. In areas where the drill hole came close to old tailings, the low results are explained as being diluted by those tailings ("intercepted by tailings"). The purpose of that drilling was not to specifically determine the quantity of spodumene/lithium in the tailings dam/s. The grades, as obtained by drilling, in tailings dams, are pretty consistent, because when tailings are deposited, they fan out from the perimeter of the tailings dam, forming a multitude of layers, maybe a couple of centimetres per week. There might have been a bad day, when the spirals were blocked up with mica, causing loss of product, but drilling will not pick up that one bad day.
If anybody still believes that the 1.5m tonnes of tailings is economic, they'd be wise to ask the question why they were not treated over 12 months ago, when AMAL/TAW first moved back onto site.