Spacing is critical. I would not want to depend on the wood shrinking.
My house has a deck w/o spacking and it does not drain like it should and is difficult to keep clean.
Our Ipe dock was not spaced properly and we have a couple boards buckling. When I pulled up some decking to install a jetski port, it was very difficult to get the boards back down. Literally had to use a sledge to knock them back in. Luckily Ipe is so hard the sledge didn't make any dents!
Lake Blue Ridge