TurboTax collects the information about the former spouse but it is only applied if your separation falls under the 90 day rule. In order to claim separated and not have the ex-spouse's income included in tax calculations, you must be separated for more than 90 days. There's no pro-ration; the former spouse's income is either considered or it's not applied at all.
So, if you were separated for more than 90 days in 2018, the income won't come into play at all. However the info is required to proceed in your return.
