@zas
So far, you can unset pretty much every tag you deem useless, this tag doesn't allow you to do that and (if you ask me) the tagging time does not provide any real value (I doubt you could find much software that lets you access it in anything other than a "just show me every tag in this file" kind of way).

@Sophist-UK 
AFAIK nothing in the ID3 standard requires us to write each and every frame we can.