I am migrating Excel Documents into Line of Business application into web pages. Which means everything excel can do, my client expect the telerik controls to do!

In your RadGantt controls, the Left hand side of the control is perceived to be a RadGrid this it is expected to have the same affordances of radGrid.
Which means that I expect the 
<CommandItemSettings ShowAddNewRecordButton="false" />
to work.

Which means I can apply all my learning of radGrid to the left hand side of radGantt.