Dying while in F1 mode voids all items but armor

I made one of these a while ago, but its still not fixed and happened to me today. I was flying while in f1 trying to take a screenshot, I hit, in f1, and died. 

I respawned and found my items, only to find xp and armor. All my items are voided. I had all netherite tools, enchanted, and shulkers full of smooth stone and concrete for my base.

This has happened to me before and I am distressed that It has not been fixed. 

Why would this even happen?