After I gave it another go - I've got a few new thoughts on what I'm experiencing. For starters - what I might describe as not gripping my heels as tightly as they could might be because they are 'road shoes' with full carbon soles. These soles are ultra rigid vs my SiDi SPD shoes. What I'm describing as a little 'loose' is when I try to walk in them the soles don't have any flex so they lift at the heel and there is some lift. When I walk in the SiDi's they aren't as stiff for one thing so there is some flex and they have lugs on the bottom like regular shoes that sort of help the shoe to rock forward and it alleviates that lift in the heel. Walking in cycling shoes is probably not any way to gauge how they should fit in the first place, but since I can't really put cleats on the new shoes to try them cycling first that's about my only reference.
For my purpose of riding longer distances and not racing closed course (or whatever might require a race fit) I'm not sure these aren't perfectly suitable. They have plenty of room in the front and ankle to be tightened down so far as I can tell. I'm not sure exactly how much more they can go, but they look like they aren't even close to being fully cinched up. My SiDi's require me to pull the ratchet as far as it can go to keep them fully snug, but they seem to work and I sometimes loosen them up a notch or so after some miles.