Potentially expensive operations are done during WT shutdown, but by that point gathering storage engine statistics for ftdc is no longer possible, making diagnosis of problems encountered during shutdown in the field difficult or impossible.

Since we already trigger the normal checkpoints in the integration layer, could we also do the final checkpoint there?

That's certainly possible, but it's a non-trivial architectural change. I'd be hesitant to make it at this stage in the 4.4 release but would be happy to explore in depth after the 4.4.0 release.