From my reading, I was under the impression sinking screws into end grain actually isn’t as strong due to how the fibers in the wood run? Like screwing into the end of a box of straws. Also from what I’ve read (granted, from the internet), pocket screws actually have quite a high holding capacity in all but one direction. I’m not too worried about that one weak direction as for a queen size bed constructed as above I feel like there should be plenty of material/fasteners/glue to keep it sturdy.
You are correct that a long-grain to end-grain joint isn’t as strong as joining long-grain to long-grain. But is it strong enough? It is strong enough if you use longer coarse screws. And really, all you’re doing with the screws is clamping until the glue dries. Today’s glues are stronger than the wood such that when you go to break it, the joint usually won’t break, it will break in the wood grain. And for PL Premium 3X, and we use it for our commercial home theater subwoofers, we let it cure for 24 hours before we remove the clamps. We do not use fasteners at all, just the glue, and we’ve had no issues at all. And our subs are 18” and 24” driven by 4,000 continuous watts so the enclosures deal with some force.