zfs question about atime update

hi,

our zfs has a logic to flush atime updates in zfs_netbsd_sync:
>       /*
>        * On NetBSD, we need to push out atime updates.  Solaris does
>        * this during VOP_INACTIVE, but that does not work well with the
>        * BSD VFS, so we do it in batch here.
>        */

does anyone here remember why it "doesn't work well with the BSD VFS"?

i'm running a kernel with a local patch to put it back to VOP_INACTIVE.
i haven't noticed anything wrong with it so far.