It is intentional. All predefined albums, that Photos is creating for us, are having a fixed sort order, specific for each album. Instead off offering us many sort options, Photos is providing several albums - some are sorted by the capture date, some are sorted by the date of import or date of adding them. And we are supposed to view the photos in the album that is sorted the way we want. or use the Years, Months, Days to jump quickly to the time we want.
As a work-around: To see your photos sorted by the date taken, descending, you may want to create your own album from your recent photos. The items in our own albums can be sorted by the date taken, ascending and descending.
And you may want to send a feature request to Apple to add sort options to the predefined albums. You can use the feedback form: Photos for iOS - Feedback - Apple
Here in the user-to-user forums, you cannot be sure, that the developer team will see your request, but they will see any feedback sent back using the form.