The Reason page_types.php defined a global variables called _reason_deprecated_page_types. The contents were a mixed bag of page_type and module names. The code that used this variable (content_managers/minisite_page.php and scripts/view_page_types.php) treated the contents of the array as if it was a list of modules and not page types ...
So - page_types.php now defines an array _reason_deprecated_modules, that has the same contents that _reason_deprecated_page_types used to have, as well as some other deprecated modules that had been left out.
A page type is now considered deprecated if it uses a deprecated module. The minisite_page content manager should now more accurately show page types that are deprecated.
This change is unlikely to cause any problems for custom code unless you ever used _reason_deprecated_page_types - which was never in fact an accurate list of deprecated page types.