FWIW, it does work if you put code in the form's Refresh() to set the OptionButton values based on the field value,

IF myfield = .t.
	thisform.optiongroup3.option1.Value = 1
	thisform.optiongroup3.option2.Value = 0
ELSE
	thisform.optiongroup3.option2.Value = 1
	thisform.optiongroup3.option1.Value = 0
ENDIF

and more code in the OptionGroup.InteractiveChange method to modify the field if the Optionbuttons have changed.

DO CASE
CASE this.option1.Value = 1 AND myfield= .f.  && Yes button
	replace myfield WITH .t.
CASE this.option2.Value = 1 AND myfield = .t.  && No button
	replace myfield WITH .f.
OTHERWISE
	* field doesn't need changing
ENDCASE
			
thisform.Refresh()

But without bound data, the control is just a flag. It seems like there ought to be a better way--and there probably is: it's called a checkbox, but the client wants OptionButtons (and they're going to pay for them!)