Of course, it’s not like back when Thor: The Dark World was being made that Kevin Feige and the other MCU bigwigs knew that an Asgardian Soul Forge would be connected to the Quantum Realm.
Just like the Dark Dimension seen in Doctor Strange, the laws of nature don’t work in the Quantum Realm like they do in our plane of existence.
Then again, given how far ahead these movies are planned, maybe they did know.
You can’t quantity or measure a soul here, but in the Quantum Realm, they have actual form, and that’s where we’ll find the people who disappeared at the end of Avengers: Infinity War.