<<who select Married Filing Jointly,>>
the last line of your post is significant.
While I appreciate your position and frustration, Congress in the CARES act wanted to make sure taxpayer money only went to those who had legal and permanent right to be here and the SS# was the way to control for that. Again, the taxpayer is footing the bill for these stimulus payments.
Every married taxpayer has the right to file either married-joint or married-separate. Any couple where one has an SS# and other has an ITIN can file 'married-separate' and in that manner the person with the SS# would be eligible for up to the $1200 stimulus payment.
There simply is no requirement to file 'joint'; there is only a requirement to file 'married' if you are legally married.
