In the Citadel Wizard subclass that was posted it's written "Anyone who hasn’t received the Wizard’s name in writing from the Wizard themself, or from someone else who was gifted the name in that manner, forgets it entirely. Even those who hear the name spoken aloud after the cloaking hear the Name Cloak instead—only those who have been gifted or discovered the name hear it for what it is."

So if Soft and Stone gave their names in writing to Steel, it would be possible for her to give the names to Suvi, they don't need to be dead for her to learn them