I think it is not a bug of the package. But it is definitely not severity grave as Akonadi is perfectly usable here in exact the same version (usable to the extent Akonadi works reliable, but that is an upstream issue). So downgrading severity to normal.
When only akonadi-backend-sqlite is installed as you can see in installed packages I find normal that the default config file is changed to use sqlite by default as I would expect that removing akonadi-backend-mysql would remove the mysql backend if it was used with a warning.
But apparently, you are more interested in having the package without bug than working to simplify your user's life.
-- eric
