The Heat and Humidity in Florida could potentially ruin things inside the building or cost a fortune to climate control until they are ready for the install. If this were true, they wouldn't have started working on the canopy. I think a lot is riding on how soon the COVID situation improves and travel bookings to WDW. Also it will probably be easier to work on the interior of the building if it is climate controlled in the summer when you get daily thunderstorms vs the exterior. Construction crews can't work outside in the rain.