Since Ted has emphasized that data=ordered is about security, not integrity, I think the point is that as long as blocks have not been allocated, there is no risk of exposure of stale data. Hence the security guarantee of ext4 data=ordered is equivalent to the security guarantee in ext3.
But frankly, since the dawn of ext3 in the 2.2.x kernel series, I've always considered the fact that it didn't leave garbage files around on my laptop (with its dodgy IDE chipset) to be its major benefit. And I never really seriously considered using the other journalling filesystems that only preserve meta-data integrity. So I am unhappy with the choice of names for the options. I'd rather that the default be "data=delayed", and "data=ordered" refer to the allocate-on-commit behavior.