It should work fine. Although I've found they make good logs for Oyster Mushroom cultivation, and fungally inoculated wood tends to work better for a growing substrate in the garden. I'd buy a bag of plug spawn and make some mushroom logs, let them produce for you for a couple of years, then use the spongy remains of the logs to build your beds. At that point, they'll retain moisture better and have lots of small air pockets (not so much as to cause a soil cave-in as the rot, but enough to be good for root systems).
