Absolutely. Being trained for such short intervals, I wonder how much their power output would drop in the final 200m after that 5 mile buildup. In any case, there has to be some optimal cyclist build for this event. I suspect it's probably somewhere between a time trialist and a pure sprinter.
Would it be within the rules to include a power capturing mechanism like a flywheel or spring that can be unleashed at the end? That would change the game to maximizing total energy output over the 5 miles, and make the whole section count.
Even without reading the rules - no. Otherwise, why not spend 8 hours to go the 5 miles, charging up the system the whole time, and get a brief burst of 100+ mph at the end? It'll end up seeing who can build the better power capturing mechanism, not seeing how fast a human powered vehicle can go.