I was curious about that when I needed it a year ago. It was low, but held air. Only drove about 2 miles to the local Wheel Works (Firestone). They honored the warranty and gave me a new Bridgestone Dueller(?) for next to nothing. I have FJ wheels....So, effectively, you don’t have a spare. A 23 year old tire may, or may not, hold air when you put a load on it.
But your point is well taken. Maybe I should consider replacing the ancient spare.... I love this truck. It is the best tool I own.