The generation number v2 is better for algorithmic reasons, but it is
backwards-compatible with version 1 and in doing so requires reading
more data from disk. That extra data load causes a performance
degradation in the typical case.
Let's avoid that for now, until a non-backwards-compatible version is
ready that avoids this performance problem.
This didn't quite make it in before the release branch was created.
The generation number v2 is better for algorithmic reasons, but it is backwards-compatible with version 1 and in doing so requires reading more data from disk. That extra data load causes a performance degradation in the typical case.
Let's avoid that for now, until a non-backwards-compatible version is ready that avoids this performance problem.