That is how they start to open the floodgates to the real thing. No exceptions.
Well, it depends if the person has self-control or not and has been exposed to the fiction. If the person is addicted to it and has no self-control (like mental health problems), the floodgates to the real thing will definitely open. It's sometimes hard to tell when one has no self-control, however, until it's too late.
However, keep in mind, not everyone becomes a pedophile in the same way. After all, porn in general (so that includes lolicon/shotacon/proshipper content) is banned in many countries, even though a lot of them have huge pedophilia and sexual abuse problems. Take Iran, for example. Pornography is illegal in Iran, but the minimum age for girls to get married is 13 and it has a shockingly high rate of sexual violence. - almost half of Iranian married women have suffered sexual violence. Also, the Quran has themes of pedophilia, with Muhammad marrying Aisha when she was a child. South Africa has the highest rape and pedophilia rates in the world, despite the country limiting online access to pornography online.
Character ships and anime do not cause pedophilia, but they can be a pipeline to it. And the floodgates can be opened by them. They're not the cause for the floodgates to open, but they can be one of them. My point is, lolicon/shotacon becomes a key for the floodgates if the wrong person is exposed to it and gets into it, but it isn't the only key that exists, unfortunately.