You're still assuming "we know" stuff we don't know.

"Yet she allowed the one who wasn't to bear the responsibility." For all we know she could have believed he probably was the father.

"At the point of discovering that she is pregnant there is no relationship between the child and either possible father." For all we know she were married at the time to the chewing-gum man. In fact Wolfgang specifically left this possibility open.

"Taking risks with kids, their futures and their happiness is completely unjustifiable." Either way would have been likely to involve a risk. We don't know which risk would have seemed greater.

"It's a wise child that knows its own father". The point I saw as relevant was, the saying is a reminder that this happens very often, and always has happened. And, unlike murder and stealing (in most cases), I'd see this kind of deception as, in principle, justifiable. That means, there are times when I think it would be the right thing to do.

What's changed is that now there are DNA test which can reveal things that in former times would have stayed hidden. I'd see that as a very doubtful advance, from the point of view of children in this situation. And if the courts put barriers in the way of making use of this technology in ways that could harm children, good on them.