About [[MediaWiki:Pagetriage-info-timestamp-date-format/en]] and [[MediaWiki:Pagetriage-creation-dateformat/en]]
Fragment of a discussion from Translating talk:MediaWiki
Looks like my initial assumption that it uses MediaWiki date formatting was wrong, so my suggestions were wrong too.
I already opened a bug about it: Bug 39379 - PageTriage uses custom date formatting.