I think there are good arguments for claiming porn is more harmful than actual sex at that age, or at least some types or porn.
I agree that if the aim of the legislation was really to stop kids watching porn it would be better served by making it mandatory for ISPs to provide filtered connections for households with minors and filtered SIM cards for minors.
Without thinking about it too deeply, that does sound reasonable. Was that ever discussed? Why was it not, or was rejected?
Its not in wide use, and I think most people do not know its an option and it has no lobby group pushing for it so I am sure politicians do not know about it.