I think there isn't any flag that can do this. Maybe a place for wish list item, I think the flag should be similarly configurable as the interactive version which asks to remove refs, formula or cancel (I would maybe add Throw also).
Names Default To Here(1);
dt = Open("$SAMPLE_DATA/Big Class.jmp");
dt << New Column("f", Numeric, Continuous, Formula(:height*weight));
dt << Delete Columns({"height", "weight"});
Will print to log:
Cannot delete the selected columns while some are referenced by the formulas of remaining columns.
Removing a formula leaves the data unchanged. Removing references replaces each reference with an empty value. These effects are permanent and cannot be undone.
Scriptable[]
You could capture this message with Log Capture() and then perform some JSL tricks to remove references / formulas beforehand.
-Jarmo