EZ Jet doesn’t operate -800 aircraft. The smaller 737s are not subject to center of gravity do to random passenger seating.
The -800 and -900 are subject to localizing, if you will passengers to more of a central location within the aircraft during takeoffs and landings so the aircraft remains within its approved center of gravity envelope.
Ryanair is not exclusive to this seating restriction when the passenger loads are light.
Airlines that have a first and or business section such as Continental Airlines, Alaska Airlines, American Airlines, and Delta to name a few, must block off the last few rows in coach when passengers loads are light even with assigned passenger seating.
This is of course the choice of the airline, but a Boeing requirement.