Your post contains a bit of misinformation regarding dining hours aboard Princess vessels.
Aboard MV Sea Princess (and her three sisters), lunch is available all afternoon in at least three places.
>> The Horizon Court serves the lunch/dinner buffet from 11:30 AM until it converts to bistro service in the evening, though only one serving area operates during off-peak hours.
>> The outdoor grill on the Lido deck just forward of the main pool area operates daily from noon until 5:00 PM.
>> The pizzeria at the top of the atrium is open daily from noon until 5:00 PM in addition to its evening hours.
In addition, there's afternoon tea, which includes finger sandwiches and scones, in one of the main dining rooms from 3:30 until 4:30. This is an excellent option if you return to the ship after normal lunch hour and don't want a heavy meal.