The issue is a change in the ENC output between the array (which was alphabetical) and the hash (which is effectively random) causes Puppet to parse manifests in a different order. In this case, a hosts::server class referenced a variable in hosts, but didn't explicitly include hosts. When the ENC output order changed, hosts::server was parsed first and couldn't resolve the variable. The fix is a manifest change to explicitly include it.

Roman's argument is that this is a bad default if it can cause behavioural changes during upgrades.

I think this should definitely be enabled for fresh installs, but can possibly see the argument for an upgrade. I'd much rather it was left on and documented in release notes with other breaking changes.

This bug has no meaning anymore, development went ahead that point.