I have been experimenting with this. Yes, it appears to be possible although I do not know exactly how or why it works.
It seems if you delete the _len[x|y|z]_nominal attributes then do a redraw, the DC uses its actual dimensions again.
The following code adds a right-click menu named “DC Actual Size” to components when right-clicked on.
UI.add_context_menu_handler do |menu|
ins = Sketchup.active_model.selection[0]
if ins && ins.class == Sketchup::ComponentInstance && ins.definition.attribute_dictionary("dynamic_attributes")
menu.add_item("DC Actual Size") do
%w(x y z).each {|a|
ins.definition.delete_attribute("dynamic_attributes", "_len#{a}_nominal")
}
$dc_observers.get_latest_class.redraw_with_undo(ins)
end
end
end