A few things, first keep in mind if you get a delay you can cancel, try again later, or take your business elsewhere - nothing wrong with that.
The shop I do 100% of my business with today, who is mostly a custom AR shop, as a policy does not transfer upon default proceed - at least not after just 72 hours of it. Why? Well they have been burned by a denial later where they are behooved to start calling and trying to get the person to return the gun, ATF may get involved - looks bad if it goes public, not that they did anything wrong but some FFLs feel a responsibility if they sold a gun to an actual bad guy (not that most PPs are bad guys really but some are)..
Me personally, I own lots of guns - one more is just gravy. If I get a delay Id rather wait and send a lawyer off questioning the gun line folks for answers (ie during a NH pistol purchase) versus running the risk of taking the gun and having some mistake be made later where the ATF, or worse local cops, might try to sneak up on me and will end up taking all my guns, ammo, mags, who knows what. A delay can mean they think something isnt right - Id rather have confirmation Im good to go, or have them deny me knowing I didnt get the gun, versus leaving things to chance later.