Thanks @flixr for reporting. We had the discussion on the github ticket but I will summarize here for visibility:
Yes it was an oversight and I apologize for the breakage and trouble it caused.
We try not to break ABI in low level packages as much as possible. As pointed out above there is not much that can be done now as the ABI breakage has been released (and that some distribution use this ABI for several months now.
That being said all the ROS tools and infrastructure assume ABI incompatibility and every package is rebuilt if one of their dependency changes. So package consumer should not assume ABI compatibility, and assume they have to rebuild the debs on top of the released ones after a sync.
A new package format has been proposed to allow packages to provide “compatibility version” information. We plan in the future to support that format in our tools and to provide infrastructure to check ABI and reject releases if a package is advertised as ABI compatible but is not. Note that this will be an opt-in choice and that package maintainers can choose to release ABI breaking changes anyway.