Just because there is a working project it doesn't mean you can't or shouldn't use escrow, have you heard of 2/3 multisig yeah? Easy stuff
The very point of using escrow is to make sure the devs deliver the product before money is released from escrow. We already have a fully functional product. We have invested lots of time and effort in it and we are not going to bail on it. There is literally no value in involving an escrow agent in a project that is so far in its development.