I expect that the designers confined these classes to implementation sections to ensure that other developers were not able to use them.
Does it change in newer versions of delphi?
In XE3, and presumably in all other versions since Delphi 7, these types are still confined to the implementation section of DBReg
.
Is it a good practice if I just copy it to my unit?
No it would not–that would be a clear violation of the Delphi license.