The text treats tablīgh and ighrāq as generally acceptable forms of intensification. They differ in relation to ordinary occurrence, but neither necessarily asserts a contradiction at the level of reason.
Ghulūw bears an additional rhetorical burden. Forms such as “yakādu,” “law,” or an especially effective imaginative scene may bring an impossible image nearer to literary acceptance.
This does not mean that any occurrence of “if” or any startling image guarantees fine rhetoric. The device must actually make the hyperbole fitting and effective in its particular context.