If there is no FM entry, then how you will perform a carry-forward?
I didn't deal with standard payment requests, though. All the projects I was involved, there were some modifications done for payment request encumbrance and there was a FI document behind with a proper entry in FM. From you screen shot, I cannot say if there is FM assignment or not: I guess, it should be in 'Acct assignment' button.
Still, if you are hesitating to modify the standard, pose a question to OSS first.