Yes, it would make the archive immutable, but that doesn't prevent the data from being deleted. A very similar example is found in git repos: while normally yo

Yes, it would make the archive immutable, but that doesn't prevent the data from being deleted. A very similar example is found in git repos: while normally you'd have every single bit of data that lead up to git HEAD, you can use git in "shallow" mode, which only has a subset of that data. If you delete all but the shallow checkouts, the missing data will be gone forever. The missing data is still protected from being modified by the hashing that Git does - and you're guaranteed to know that data is in fact missing - but that cryptography doesn't magically make the data actually accessible.