This just showed up this morning, in a DP 4.2.1 release page:
"ODBC Connections
The purpose of the ODBC provider is to offer basic connection and querying capabilities to any database that supports an ODBC 3.0 or later driver. For a list of databases tested with the ODBC provider, see the System Requirements in the Release Notes. This form of connectivity allows connections to databases such as Netezza, IBM iSeries, Ingres, and Vertica™. Because this form of connectivity is generic, it is not full-featured and may not be as robust as the fully-exploited providers for the other databases."
Unfortunately this might mean that the lack of the SQL button is not a bug but just how DP implements ODBC connectivity.