Hi!
To my understanding, you are re-using Apache directive names so that Apache users understand their meaning right away.
A too little known (while documented) thing about AddType in Apache is that a call
AddType application/x-httpd-cgi cgi
in Apache would have ".cgi" matched in "index.cgi.png", not just at the very end.
The latest Apache docs on AddType say
Filenames may have multiple extensions and the extension argument will be compared against each of them.
about it and point to the notes on multiple extensions.
Due to its security implications, it could be considered a good thing that Boa does not duplicate this behavior. Since you do have a section "Unexpected behavior" in the Boa documentation, I would ask to add a paragraph documenting that difference to Apache's AddType directive. What do you think?
Best, Sebastian