It does not address the problem that people assume that the "changed:"
attribute actually properly identifies when an object was changed. If
this is desired, then the attribute should be made mandatory, and the
timestamp always added by the server. In the past, there has been
opposition to this idea.
Your suggestion does have merit. If people want to tag the changed
line they can do and for those of us who don't we just see when it
was (possibly) last changed.