Deprovision removes all modifications?

I'm starting with Ubuntu 18.04 cloud image and adding my modifications. Then, when finished, I perform the deprovision+user. When I upload my VHD and create a VM from it, my changes have all been removed. I had created a new systemd service, I had files in /opt that are gone. Help me understand what deprovision does. I didn't think it would have removed everything.

Start with the deprovision+user workflow described for an Ubuntu 18.04 cloud image and compare the resulting VHD with the original, checking the new systemd service and files under /opt. Done means determining whether this removal is expected and clearly explaining which modifications deprovision preserves or removes when the VHD is used to create a VM.

Written by the indexing model from the issue text.