About the grace period when VPP application licenses are not assigned

After assigning VPP application license and installing the app in device, I revoked the license while it was still installed. However, I was able to use the app even after 30 days. I think this app is not available in ASM(Apple School Manager) specification. Is this specification applied in ABM(Apple Business Manager)?

I found this discription in ASM, but I couldn't find it in ABM. https://www.apple.com/au/education/docs/VPP_Education_Guide_EN_Oct13.pdf

“When apps you’ve assigned are no longer needed by a user, you can revoke and reassign them to different users. The user gets a 30-day grace period to continue to use the app, save data, or buy a personal copy. ”

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Revoking a VPP license is only one part of the process. Each app must also check its receipt periodically to ensure that it is still licensed. If the app doesn’t check its receipt, it may continue to function after its license expires.

Details for app developers: Validating App Store Receipts