When we harvested the 20-year-old tree which was used for the Crassna Cha Experiment, I picked up a fresh piece of heartwood that smelled like the fanciest feta cheese I've ever had the pleasure of smelling (
click to see). The scent was extremely fecal, yet incredibly satisfying. One day later, our hotel room began to reek of fecalicious funk to such a degree that it was too much to handle. So I put the chunk of wood into a ziplock bag. Within two days, the entire bag was filled with fungus. White hairy mush grew out of the still moist agarwood which eventually started to turn green like proper mold. At that point, I had to discard it.
Long story short, it is very possible for fungus to appear on a piece of oud wood which is not 100% dry, if it is sealed in an airtight container, like a ziplock bag.
FYI, I store all oud wood in the freezer. In arid climates (like Jordan) the oleoresins can escape from the wood very easily, and you can lose considerable weight as well as aromatic oleoresins. My practice has been to always seal the wood in saran wrap, then freeze it until it's time to fumigate.