re: My opinion is that
The effect of gravitational field is all persuasive and instantaneous, it does not propagate in the manner that photons do.
In a hypothetical situation where a photon existed outside a gravitational field and was stationery in relation to the gravitational field, there would be no effect on the photon, but when the photon accelerated and moved into the field, then as soon as it encounters the field it would be affected by the field.
In other words it is the acceleration and speed of the photons (or mass) that determines the time delay of the effect.