My approach to stuff like this is basically semver: the product is out, so any new capability (e.g. parallel operation) can't change the default at least until a major version change.
This is true for post 1.0.0 versions. 0.Y.Z versions are experimental and the API has not been stabilized yet.
Ah right. I didn't even look at the current version number I must admit (and my own practice is that stuff starts at 1.0.0), so I didn't consider the pre-1.0 clause.
I always start at 0.1.0 until I figure things out :)