As I have said before, the line that specifies Enterprise's gross tonnage as nearly a million versus its stated mass of 180,000 is likely referring to denenerate matter held for conversion to consumibles for crew and ship. 800,000 tons of it. Enough for the mission and more if needed. So yeah. Maybe.
As for ignoring the "five year" part, sure, whatever. It's there. It's stated. You can finesse it with the deft touch of a fan trying to make 800,000 tons fit in a 180,000 ton ship, but Occam and all. Do we assume he says it but that he really didn't have a "five year mission" or that he said it and did have a "five year mission"? To each his own.