While this is unusual, it's not completely impossible. If one spouse itemizes you have to make sure to force the other spouse to itemize. You're not allowed to use itemized deductions on one return and a standard deduction on the other.
I see this once in a while if one spouse has large medical expenses (then you're losing 7.5% of a smaller AGI number by filing MFS). Pre-TCJA it might also be triggered by 2106 expenses (2% of a smaller AGI) and there were some cases involving child tax credit (before they raised the AGI limit to $400K).