Question re: loan payment married filing jointly vs separately

Hi all I’m using the student aid.gov. loan calculator to calculate my estimated monthly loan payment if I file taxes jointly versus separately. The calculator is showing the same monthly payment for IBR whether I file jointly or separately – is it strange that it’d be the same amount? If this is correct I’m inclined to file jointly but assumed my monthly payment would be lower if filed separately so wondering if the calculator is misleading me…

For context, I make 180k and my spouse makes 80k/ year. I am pursuing PSLF and have about 1 year until I can apply for buyback.

Thanks for any insight!