This thread was not about deductions, but about the government pre-filling your tax-returns with data it already has about you. Parent was implying that does not exist in Germany, which isn't true. Or are you actually saying that the government will deliberately fill in wrong values, so that you have to pay higher taxes, even though the prefilled values are visible to you and discrepancies would be obvious (and a huge scandal).

There are several ways in which a software can fill data "wrongly".

If you are legally able to claim deductions, pre-filled tax forms that do not contain those deductions are by definition wrong, even though you may agree with individual form items. While this can be related to innocent mistakes and the sheer inability of the state to know the necessary information, sometimes it appears to be deliberate: The classic example is the Pendlerpauschale, which does not appear in Elster pre-filled tax forms even though the state does have all necessary information (address of your flat / address of your employer) to fill it.

If you accept these faulty forms, you will almost always pay more taxes than you have to.