This one falls into the "obvious in retrospect" (headbang) category.

In gst-plugins-good, ./configure --help says:
[... stuff]
  --disable-debug         disable addition of -g debugging info
[... more stuff]
  --disable-debug         disable dependency-less debug plugin

Oops.

'./configure --disable-debug --with-plugins=debug' does what it's told, but certainly not what you'd expect. This is most frustrating.

This issue appears to have been introduced in 0.10.8 when configure.ac started using AG_GST_CHECK_PLUGIN for dependency-less plugins.

The only marginally sane change that I can think of would be to e.g., rename gst-plugins-good/gst/debug to gst-plugins-good/gst/gstdebug, so that the debug plugin's subdir name doesn't cause a conflict with the standard --disable-debug argument.