oddity with :noautocmd when editing a help file

[Benji Fisher]

     Bug or feature?  While editing this e-mail,

:set ft=log

:set ft? syntax?
  filetype=log
  syntax=log

:noa e!
"/tmp/mutt-localhost-19331-88" 
"/tmp/mutt-localhost-19331-88" 7L, 108C

:set ft? syntax?
  filetype=log
  syntax=log

as expected.  While editing a help file,

:set ft=log

:set ft? syntax?
  filetype=log
  syntax=log

:noa e!
"autocmd.txt" 
"autocmd.txt" [readonly] 1260L, 52535C

:set ft? syntax?
  filetype=help
  syntax=log

How did 'filetype' get set to "help"?

                                        --Benji Fisher