Today's rate for 30 year fixed is the BEST this year (at least for this particular lender), although it is still 4.000%. Today I could do jumbo conforming loan (<=$625K) at 4.375% No Point No Fee with LTV <= 80%, not 75%
I think it is highly doubtful that Chase relies on the last name being the same to make such important decisions. they must have a magic formula that considers various factors such as address, credit report, public records, etc.