Looking at source of `org-html--build-pre/postamble`, I think `:html-postamble t` does check `org-html-postamble-format`, but I'd like it to check `:html-postamble-format` as well.
I encountered this problem as I'm trying to remove the validate string in the postamble, which `:html-postamble auto` will always include. Not sure if there's a way to still keep the result of `:time-stamp-file` with `:html-postamble t`. That is, retain the inserted `Created: ...` string. -- Brady
