4 years of 50% production isn't that bad of a ramp-up period and...

4 years of 50% production isn't that bad of a ramp-up period and means the second stage can be expanded via cash flow.

Your assumption is pretty broad brushed (4 years production is not a plus) and could definitely be wrong depending on the mine plan, site plans, capital requirements and project NPV.

Without reading the Full DFS document you don't know what factors influenced that decision and thus you're just throwing up a guess and assuming you're correct. Not the way it works I'm afraid.