This was an idea put forward by the founder of YBR about 8 months ago. The idea was to abstain from masturbation as much as possible, but if you got a bad urge to look at porn, then you should masturbate rather than looking at porn. The only rule there was to never ever look at any porn. This way they could disassociate porn from masturbation and make it easier to deal with each one by itself. They've since changed their mind.
The thing is this: they are goyim and did't think that masturbation was wrong. They don't think that it is morally wrong at least. But we are Jews. Hashem tells us not to look at porn or masturbate and that is what we should do. And if He wants us to do it, He surely gives us the strength to do it. We don't have to limit ourselves to be as good as a good goy when we can be as good as Moshe rabeinu.
Certainly you're right that if the aveira was definitely going to happen, it's better to masturbate without porn than with. The problem with this mentality is that it gives you permission to sometimes masturbate. As soon as you give yourself permission, it is bound to happen, whether it was necessary or not.
The other problem is as 'Blind beggar' said is that masturbation feeds the urge to look at porn. It takes away the urge for a few minutes only, after that the urges come back stronger. It's called the 'chaser effect,' or in Jewish ''there is a small eiver in each man, feed it and it will starve you, starve it and it will feed you.'' And in pirkei ovos last week ''aveiroh goreres aveiroh...schar averiroh aveiroh''
The reason why I mentioned YBR is that even they now agree that you cannot beat porn by itself. You can't do everything except watching porn and make progress. They now reject the idea and say that to get over porn addiction you must stay away from porn, masturbation, edging, fantasy, and any picture or video that is arousing.
It sounds like that makes it harder, but ironically it's much easier. The point at which you're touching yourself is really too late to fight it. Yes, sometimes you can win even from there but your chances are not as good. The battle ground is not there, but much earlier, when you first had the inkling of an idea that you might want to look at porn. That's the time to fight and it's much easier.
Learn to dismiss thoughts of porn and masturbation as quickly as you can, and you'll find yourself in fewer situations where you even need self-control. That's true yiras shomayim. Hashem should help us both in this.