Right before you go live in a production environment, some partners reset an instance and then layer their solutions on top of the newly created instance. And the version numbers of solutions as well as the actual solutions installed may differ from the instance before the reset.
Why? Every time you reset an instance, the Dynamics 365 service treats the instance like a brand new instance, which it is.
If you have a instance that you want to maintain all of the exact same solution versions and not have new solutions added to it like would happen for a new customer, you should backup the instance and then copy it. Doing that the Dynamics 365 Service Engineering team doesn’t treat your instance like a brand new one.
More data on Reset and Copy is available on the Microsoft Docs Site.