Apple Books: What does the "Transfer" option change during 90-day device association?

Hello,

I am hoping someone familiar with Apple Books, Family Sharing, and device association can explain the expected behavior.

I have a shared iPad (7th generation, iPadOS 18.7.9).

The iPad is configured as follows:

• iCloud Apple Account: My wife's Apple Account
• Media & Purchases Apple Account: My Apple Account
• Family Sharing: Enabled
• Purchase Sharing: Enabled

This configuration is intentional and has been working correctly for Photos, iCloud, Family Sharing, and Apple Books until this issue occurred.

Here is what I have verified:

• Wife purchased "It Could Have Been Her" by Lisa Jewell through Apple Books.
• The purchase appears in reportaproblem.apple.com under Wife's Apple Account.
• The book is not listed in Hidden Purchases.
• In Apple Books, I can navigate to:
• Profile → Family Purchases → Wife → Recent Purchases.
• The book appears there with a cloud download icon.

When I tap the cloud download icon, the iPad displays this message:

"This device is already associated with an Apple Account. If you download past purchases with your Apple Account, you cannot auto-download or download past purchases with a different Apple Account for 90 days."

The choices are Cancel and Transfer.

My questions are:

• What exactly does the Transfer option change?
• Does it affect only this iPad, or any of my other Apple devices?
• If I select Transfer, will my Wife still be able to download her own Apple Books purchases while remaining signed into her own iCloud Apple Account?
• Does Transfer affect Family Sharing or Purchase Sharing?
• Is this the expected behavior for an iPad using one Apple Account for iCloud and a different Apple Account for Media & Purchases?

I am looking for an explanation based on Apple's current behavior or documentation.

Thank you.