Form 26QB to be filed by each joint owner of a property even if not contributing financially?

I have understood that one must file Form 26QB for every combination of buyers and sellers. If there are two sellers and two buyers, four 26QB forms should be filed in all. My query is that my son bought a flat in Feb 2021 (in joint name with both parents) and he is making all the installment payments and is also paying 1% TDS by filing Form 26QB. Parents don't make any contributions and hence never filed form 26QB till now. Till now, the old website did ask about "if there are multiple buyers" but it neither asked for details of multiple buyers nor directed us to file separate form 26AS. This year, after the tax payment system shifted to the Income Tax website, we can see this change. The new website directs each buyer to file a separate form 26QB. We stopped at this point and did not proceed as we wanted to clarify this first. Should both retired parents, who don't make any contribution to installment, also file form separate 26QB? What will they write in the fields for Amount Paid (to the builder) and Tax Paid? Should not there be a distinction between Joint Owners (who may be family members not contributing financially) and Joint Buyers (those who contribute to the installments and hence must file 26QB)?