I opened up the latest snapshot in a superflat world in creative, I was building something and had a full invetory. I decided to give myself netherite leggings because I wanted to apply the new swift sneak enchantment so I could move faster. I didn't have enough room in my inventory to pick up the leggings, enchanted book, and anvil all at once, so I gave myself the enchanted book and anvil and threw the leggings on the ground, but somehow I picked up the leggings. I went to see where they were in my inventory, but they were nowhere to be seen, they weren't even automatically equipped. I tested it out a few times and can confirm that you can pick up stuff even if you have a full invetory.