I think I'm the first to find this, might save some time in current patch runs :)

Edit: apparently this was already found, now it's just a question why this isn't used in nmg current patch.

cool!

This is known, i believe gwonkee used it a couple times for impossible any%

why isnt it used in nmg current patch?

it's not as useful as current patch inventory drops usually, as dream nail drops are just as precise (1 physics frame) and your fall speed is capped again once the dream nail animation ends. You also cannot do it in the middle of a dash, contrary to inventory drops, making them take longer to set up. It's a cool piece of tech, but it just does the same as an inventory drop for a nonvariable time period (you need to wait for the animation to finish, meaning you're stuck on the ground for a while) for the only advantage being you can hit stuff with the dream nail.

Adding to what Jamie said, you can also use it to place a dreamgate at the bottom of a drop, but as far as I know, that isn't done in any main categories.