Ann: Drilling confirms large scale Lithium Brine Basin Kachi, page-36

Believe me I'm not into the technicals too much and leaving that to the guys we are paying to do just that. But, I can understand the logic of drilling to those greater depths and NRG are now also pursuing that policy.
"May 8, 2018 / Vancouver, BC / NRG Metals Inc. (“NRG” or the “Company”) (TSX-V: NGZ) (OTCQB: NRGMF) (Frankfurt: OGPN) is pleased to report that drilling at the Salar Escondido Lithium Project has progressed ahead of schedule, and an 8.5 inch rotary hole has been completed to the target depth of 400 meters. The hole will now be reamed to a diameter of 12.25 inches so that perforated casing can be installed in preparation for sampling.

LKE seem happy with drilling to even greater depths "Deeper horizons are being targeted to locate higher grades and extend the potential size of the brine mineralisation. The suggested size of the brine body has made the Company contemplate further drilling rigs to accelerate the resource statement."
I say, why not, it doesn't seem to take much longer drilling time and be good to get as much data as possible in these early days. They can refine their drilling target depths when more assay results are available to them. More data the better and with that seismic survey "could" expose an even greater productive asset than was originally imagined.
Size is king!!