While I appreciate your perspective, my thoughts are as follows:
Moving a mojoportal site means copying and moving the files and backing up and restoring the database on a different machine.
Most good hosting companies provide tools to assist with backing up a site and its database. Most database platforms include tools or tools are available for backup and restoring of databases and you don't need to know anything about the schema to use them.
A Web CMS does not need to replicate that kind of functionality, it is kind of like expecting MS Word to backup all your Word docs, they make backup software for that, it is not built into Word.
Someday I will make an add on paid product for exporting and importing mojoportal data as xml so it can be done across database platforms but it is a high end expectation to be able to do this.
There is nothing hidden about the mojoPortal database schema, you can inspect and if needed document the schema using database platform included or add on tools. I mean anyone with SQL Management tools can browse the tables and schema and/or make table diagrams.
End users do not need to be concerned with the database schema in order to backup the database. Any developer worth their salt knows how to inspect a database but I don't publish documentation about the database schema because developers should not access included tables directly, they should use the business objects and or create their own tables for custom features.
I am building software for managing web sites not for managing databases, that job is already done by the database vendors.
As far as deleting test sites that can be done from the UI either before or after restoring a backup to a new server.