One obvious reason the downturn for the SP in the Lassonde curve...

One obvious reason the downturn for the SP in the Lassonde curve is it can take a few years (eg 2-3) from the FS to production to build the plant and mining infrastructure, etc and during that time there is little or no news ( ie no drilling results that result in any significant upgrade to MRE, etc) to push the SP higher only just updates on building the plant and mine. That is no catalyst for a higher SP - hence investors go elsewhere for SP appreciation.

It will be very different for SPR given plant already exists and only needs small enhancements/modifications, tailing dam exists, other infrastructure in place, the decline from which mining takes place will be in existence, etc. They will need underground mining equipment, a paste plant, etc and mining staff, etc, we may only have to wait 6-12 before production starts and during that time they may even do a lot more drilling assays in new areas. That is the Lassone curve is far less applicable to SPR.