I do agree that the agreement's debt financing provisions may provide Musk an out -- "I wanted to close, but I couldn't get debt b/c you wouldn't cooperate".
I'm a little surprised that Twitter agreed to any sort of financing provision, precisely because it seems to allow Musk to screw up his debt raising and then point to that as an out.
But that is not a complaint in the letter, and becomes an argument about what lenders require for debt financing. Musk will have to show that lenders cared about this, and Twitter will have discovery to find evidence they didn't.