Peter, with top flange hangers beam shrinkage won’t matter, the Joists will still be in the same position relative to the top of the beam. I’ve never seen I-joists installed on a beam in which the tops of the beam and joists were supposed to be flush without using top flange hangers although I’m sure someone somewhere has decided to use up those hangers that’ve been stashed away in his garage and save $25.
All in all, we don’t have to confirm compliance to engineering. I called one roof system in which the framers had nailed truss-bearing hangers with siding nails (40% smaller diameter and a different alloy) but unless it looks bad or you know it’s wrong, why call it?
Joist layout would be called out by an engineer and it might be 12", 16", 19" or 24" on center (center to center, not in between). Unless the floor or roof exhibits exfcessive deflection, joist spacing is not our problem. If it does, then call out excessive deflection. -Kent