Lenovo Yoga Tab 3 Pro (YT3-X90L) factory image, OTA update or backup needed
I've wrote it down. Translation by google, but i think it's all good :) Sry for not posting, needed some time.

Situation:
"Confirm account: The device has been reset. To continue, sign in with a Google Account that was previously synced on this device. "

Explanation:
The device has been blocked by repeated input of the wrong password, pattern, etc. and can only be unlocked with the Google account of the owner.
A factory reset or hard reset does not help here, as the account information is saved in its own FRP partition and will not be deleted when the factory state is restored.

Solution:
1. Connect device to a Wi-Fi and Internet access.
2. Before confirming "Next", select another hotspot here
3. Go to "Advanced Settings" and change the proxy settings of any hotspot to Manual.
4. In the text input field of the proxy settings you enter now any word: e.g. Test
5. Now mark this word and select "Assist" in the context menu.
6. Selecting this "Assist" option opens the Google search application.
7. You can now not only browse the Internet through this search, but also search for and open installed programs.
8. We are looking for Chrome, open the internet browser, go to www.google.com and search for DPC test.
Link: https://www.apkmirror.com/apk/sample-developer/test-dpc/test-dpc-4-0-6-release/test-dpc-4-0-6-android-apk-download/
9. After downloading this application, go back to the Google search application.
10. Here we enter "Download" to search for the download application.
11. In Downloads we can now find and install the downloaded app.
12. To allow the installation of this .apk, you must allow the installation of "unknown sources" in the settings.
13. Either you go here on the installation itself on "Settings", or you search for "Settings" on the Google search app.
14. After completing the installation of the DPC-Test program, start it with "Open".
15. The app itself is will register as a device owner and now allows us to set up a new Google Account as owner.
16. If this is set up, it will also be included in the FRP partition.
17. In the event of a new factory reset, the device is reset, the DPC-Test program is removed and the device can be freshly set up in the factory settings.

after the takeover of the owner, the reason for blocking the device was not present anymore and the old owner was overwritten. This will be overwritten in the FRP partition aswell with the new account and the old one no longer queried.