apushatayid, Yes, assurances that they wont be stiffed might encourage shadchanim to work on such shidduchim, but that is not what NASI is saying, or how they are promoting this game changing plan.
I think it’s a matter of perspective. The main thrust here is to motivate shadchanim to work with older girls by having the girls or their parents offer higher shadchanus, and the escrow feature is a measure to ensure that there’s no manipulation and false promises by desperate people.