The new iPad Mini (6th generation) introduces a new, smaller(!), screen size?

All the early commenters are just repeating Apple's "7.9 increased to 8.3" line... no-one is mentioning that the smaller dimension has reduced from 1536 to 1488.

Hopefully the proper reviews will answer this question, but I'm interested that it's not getting mentioned.

That means they have changed the form factor.

In number of pixels:

• iPad Mini 5 : 3,145,728
• iPad Minin 6 : 3,371,808

Which is a 7% increase. So globally, there is more space, in a different format.

They say "larger" (which is true), not "wider" (which is not).

Since the iPad was introduced, I've been aiming iPad apps at a minimum dimension of 1536 (actually 768, pre-Retina).

Now, that content may not fit! Sure, but you should not target the app for a specific device. Nor assume a specific size. Just use constraints to make sure you app fits any device.

There's a good iPad Mini review by Federico Viticci, writing on MacStories.
He raises all the issues I've been wanting to talk about.

Speaking of the narrower (in Portrait orientation) screen, he says:

This has some interesting side effects on webpages and apps, and it makes using the new iPad mini a peculiar affair at first.

...and in Landscape mode:

...you get longer lines of text but fewer paragraphs of text displayed at the same time.

...and the kicker (emphasis mine)...

..I think some apps will have to be updated to properly take advantage of its new screen resolution.

Speaking of games:

...all the games I tried from Apple Arcade over the past week featured black bars (letterboxing) on the left and right sides of the display.

and (again, emphasis mine)...

...I hope game developers will update their games quickly to take advantage of the full 8.3” display on the iPad mini

Overall, the review is very positive, of course.
https://www.macstories.net/stories/ipad-mini-review-small-wonder/

And here (finally?) is Apple's statement on the need to recompile full-screen apps for the iPad Mini 6:

...if you’ve added UIRequiresFullScreen=YES to your app’s Info.plist in order to keep your app full screen during multitasking, you’ll need to recompile with Xcode 13 and the SDK for iPadOS 15 to take advantage of the full screen size

See https://developer.apple.com/news/?id=oefg5bhp&1632770922

Otherwise, your "full-screen" app will be displayed with black bars.

So the answer to my original question...

Do I really have to go back to my apps, and add scrolling, or trim the content?

For full-screen apps:

• Recompile with Xcode 13 and the SDK for iPadOS 15
• Resubmit to the App Store

Geoff Hackworth has an excellent analysis of the issues here...
"How iPad Apps Adapt to the New 8.3" iPad Mini"
https://hacknicity.medium.com/how-ipad-apps-adapt-to-the-new-8-3-ipad-mini-7796efdc88eb