The official Missed Flight Cover FAQ seems straightforward enough:
3) What does Missed Flight Cover actually insure me for?
In the event you miss your flight you will be offered either:
a) A seat ... on the next available easyJet flight to the same destination.
4) Are there any exclusions to the policy?
There are no exclusions but there are 3 simple conditions should you wish to make a claim:
a) You must be at the airport within 4 hours after the scheduled
departure time of your flight and the plane must depart.
b) You must be in a "fit state to fly";
c) You must tell the easyJet Sales Desk at the airport that you wish
to make a claim.
5) Are there any circumstances that would prevent you from paying a claim under the policy? Yes, if you fail to follow one or more of
three conditions stated in Question 4.
So the answer is yes, you can do that. However you'll have to arrive at the airport within 4 hours of the plane departure to arrange for a replacement ticket.