Looking through the documentation, it doesn't seem to explain what rights are required to access the page Special:PageTranslationDeletePage. Is it just the translation administrator right (as used locally through WMF wikis) or is it that right in combination with another right? If it is a combination (which I believe that may be), then it would be useful for the error message to say which rights are required (in combination), rather than the right that is missing. I would also note that Special:SpecialPages does seem to note this deletion page, nor can I find ready reference to its actions either. It would be great if those more knowledgeable would be able to remedy this situation. Thanks.
Topic on Help talk:Extension:Translate
Works for me on Meta (where I'm translation admin):
You do not have permission to delete this page, for the following reason:
The action you have requested is limited to users in the group: Administrators.
But yes, permissions could be checked earlier. I expanded docs a bit.
And yes, it's one of many unlisted special pages.
I have specifically mentioned the special page, otherwise it sits mute, and not findable by use of search, which I consider less than desirable.
Submitted bugzilla:66472 for listing the extension page on Special:SpecialPages