Freeing up space · Recycle Vault
How is the Recycle Vault different from my Mac's Trash?
Short answer: The Trash holds what you delete in Finder on the same disk. The Recycle Vault holds what Storage Studio removes, keeps it on your external drive so your Mac really gains space, and clears it after about 6 months.
Your Mac's Trash holds what you delete in Finder, on the same disk, until you empty it. The Recycle Vault holds what Storage Studio removes for you, and keeps those files on your external drive — so removing them actually frees your Mac — versioned and recoverable for about 6 months before clearing automatically.
Storage Studio never empties your Mac's Trash for you. See What is the Recycle Vault?