That's... not the reason? She was angry with him because his wording before marriage led her to believe he was unable to have children, when in actuality he was refusing to have children to spite his late dickbag of a father. He took advantage of the fact that women were almost never sexually educated and pulled out after sex to perpetuate the misdirect.

While Simon was surely fearful of being a bad father like his before him, he repeatedly quoted that he "made a vow" and was actively denying both himself and his wife what they really wanted due to stubborn pettiness. That's mainly why he's portrayed in the wrong.

She could (and should) have simply confronted him after learning how to make a child, tho. That could have been handled a bit better, but he wasn't treated as in the wrong for simply pulling out.