Documentation for crop needs to be updated
From the Gimp-user mailing list:
Why is it that now when I crop the image that the canvas sticks out. Why did you break this?
We did not break anything :) We added a non-destructive mode and enabled it by default.
Can you tell me the setting that returns the gimp to sanity?
Enabling the "Delete cropped pixels" checkbox in Crop tool's options restores the old destructive behavior
All of that has been documented:
https://www.gimp.org/news/2020/06/11/gimp-2-10-20-released/#basic-non-destructive-cropping
https://www.youtube.com/watch?v=6CJA8RRLWuQ
We need to update the user manual though.