Interesting that the IRC doesn't specifically prohibit a trap door in the deck, as long as there will be a 36" opening.
My 2003 IRC (too tight to buy an update every few years) doesn't have a Section R310.5, but it does state in R310.4 that "bars, grills, covers, screens or similar devices are permitted to be placed over emergency escape and rescue openings, bulkhead enclosures or window wells that serve such openings, provided the minimum net clear opening size complies with Sections R310.1.1 to R310.1.3, and such devices shall be releasable or removable from the inside without the use of a key, tool, or force greater than which is required for normal operation of the escape and rescue opening."
As others have said, it's up to the local AHJ to make a final determination. Without their blessing, things won't fly. Nor will an upward-opening deck trap door with a 300-lb. picnic table parked on top of it.