wget timestamping (-N) bug/feature?

[Bao, Jiangcheng]

Suppose I have page a.html, which has a link to b.html. If a is not
changed, and b is changed. When I process a, I have no way to check a so
that I can process b too, without downloading a. -N will cause a not to be
downloaded, but not processed either, so change of b will be ignored. If I
will -nc, then a will be processed, and b too, but b's change will still
be ignored. If a new page c is linked into b now, then c won't get
noticed.

Is this a feature or it's a bug? Thanks.

Jiangcheng Bao