It doesn’t seem as if that’s generally true.
A quick search on the subject says that a female twin with a male twin is likely be infertile. That’s called a “freemartin.” Also, a cow may reject one twin. However, the value to a farmer makes hand-rearing the second twin or placing it with another cow a financial win.
Perhaps it was the freemartin issue, I was reading about dairy farming and they want heifers!