> Thank you Dan. so changes in 1/10th indicate API changes?
Yes the first two components signify the major version.
The mysterious Backpack might be able to help with some of these things but in general it's not enough just to look at the visible API. I might require V10 of a library because it fixes a bug in a subtle way (such as changing the encoding of certain characters in a URI), or changed behavior that isn't visible in haddocks (a ToJSON instance that now produces property names in lowercase). It can be argued that both of these should be changed in a major update, but the PVP does not require this and neither can it specify breaking changes to an arbitrary level of granularity. As a maintainer I might still need to both whitelist versions I know are good and blacklist those that are not to make sure users don't get a package combination that doesn't work as expected.