The Studio uses a file called mdspgsql_DriverDef.xml that is in your DataFlex Bin folder.
By default the DAW installer puts a very basic one in there that supports the very basic things (about 5kB in size, version is probably 8.0).

When you install the driver from Mertech for your DataFlex version, it updates the DriverDef files for the Studio and the drivers.
You can then do things like change native data types for the DataFlex data type.
This (and more) is handled via that DriverDef file.
I haven't looked at it in a long time, but last one I worked on was version 12.2 from the looks of it.

There's DriverDef files for each of Mertech's drivers and you want these in place for improved support from the Studio.