May want to double check to ensure your change does not FORCE insurance on all orders when updated via edit orders (including when saving an order where the customer did not request insurance). The above runs a good likelyhood of also flipping insurance for any subsequent order as you are adding the change into the Store Admin's login session (persists beyond a single admin page / request).

May be better to update ot_insurance.php to check if the module was already part of the order and loaded via admin (and if both are true, flip the flag instead of adding to the session).