Hi,
and while going through the emacsbug.el code, I saw that the report-emacs-bug-send-hook is defined but it is not run any where.
My understanding is that you always need a run-hooks form to execute functions in a hook.
I grepped the source, but couldn't find any instance where report-emacs-bug-send-hook is run.
btw my proposed fix for this bug is to save and restore the windows configuration before and after sending/canceling a report.
And bind the cancel action (kill buffers, restore windows config) to a generic binding like "C-c C-k". The currently suggested "C-x k RET" binding will of course continue the current behavior (of closing just the message buffer and not the Bug Help buffer).