So it does not assert that the filesystem is in a consistent state before it snapshots. IE we could be midway through applying a database transaction; or there could be a reference in one file to another that doesn't exist (yet).

It could be argued that one needs to do a site wide "write cache flush", stop, and snapshot. Not that I think for one second the service provider should (or could) be in a position to detect when a good time to snapshot might be....