The geological work and drilling program required for a "pre-feasibility study" can take a couple of years. The "couple of months" is just the very tail end of the process. And then once that is complete, a feasibility study takes several additional years.
Cinco Minas never even made it to the prefeasibility stage, much less having a full feasibility study completed. And to legally claim reserves, a full feasibility study is required. A "pre-feasibility" is not acceptable.