As far as I can see all this is just changing expectations. Just a few years ago we were *happy* that our filesystems were readable after a crash (after running fsck). Then we progressed to being happy that after a crash we could use the filesystem without waiting hours for the fsck.
Now we're at the stage of worrying about exactly what the files should look like after a crash. Give it a few years and I'm sure we'll find something else to worry about. Also, POSIX was written a long time ago and deliberately vague on some points because they wanted to support many existing systems which all worked slightly differently.
NB: ISTM the solution to the 'lots of little files on ext3' problem is obvious. Create all the new files, then fsync them (fsync on ext3 may be slow, but it wouldn't be as much of a problem this way because all the data would be written out for all the files in one go). Finally rename them all.