Can't Upgrade Native Reminders App on iOS 16.5

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I sync reminders between my Macbook and the iCloud.com Reminders widget. My Macbook runs MacOS 13.2.1 and has the upgraded Reminders app. On a new iPhone 13 running iOS 16.5, I opened the Reminders app for the first time, which appears to run the old version of Reminders. There is no blue "upgrade" button available on the welcome splash screen or on the Reminders "home" page. So, the reminders I create on the Macbook or on the iCloud.com Reminders widget are not available on the phone. And reversely, the reminders I create on the phone are not available on my Macbook and are not available via the iCloud.com Reminders widget. I am confident the Reminders app running on the phone is the old version, despite my running iOS 16.5 stock with the new iPhone 13. BUT, there's no way for me to upgrade the app, even after deleting and reinstalling or erasing all content and settings. The blue "upgrade" button simply isn't there. I've confirmed all the basics: logged in the same Apple account across phone, web, and Macbook; confired iCloud sync is enabled on the phone and Macbook; removed/reinstalled the Reminders app on the phone; reset all settings; erased all content and settings.