The vast majority of programs, even when symlinks were optional, assumed
their presence, because the enormous majority of the installed base had
This is actually worse. If you get the open()/write()/fsync()/close()/
rename() sequence wrong, by leaving out the fsync(), the visible effect
during development is *nil*, even on filesystems like pre-patch ext4,
because this is a change which only has an effect when something goes
really wrong and the OS crashes or you lose power at the wrong instant,
and if that happens, any data loss will be written off to the power
failure, like as not.
Expecting any but the most skilled developers to remember that fsync()
when omitting it has *no visible negative consequence* in normal operation
is a complete and total pipe-dream. You can wish all you will, but only a
few percent will ever conform.
It is much better to arrange to do the right thing in the filesystem,
which *does* have especially skilled people hacking at it, than in the
vast mass of wildly-varying-in-quality code out there in the real world.