Plausible deniability in a vault interface means ordinary use can reveal one private space without the interface itself confirming every other space that may exist.
Interface evidence is only one kind of evidence
A master list of vault names can disclose that additional content exists. A pattern-addressed interface avoids that particular directory. This changes what a person sees during ordinary navigation, but it does not determine what can be inferred from device storage, backups, prior observations or your circumstances.
For that reason, plausible deniability is not a guarantee that another person will believe an explanation. It is especially unsuitable as a promise of safety during coercion. A person can continue demanding access even when an interface reveals nothing more.
Separate a decoy from a destructive action
An ordinary decoy vault contains material you chose to show. A duress vault can trigger a destructive action against other local vaults. Confusing these behaviors can cause irreversible loss. Learn the distinction before configuring either, and do not experiment with irreplaceable content.
NullVault's specific claim
NullVault's normal flow opens the vault selected by a pattern without displaying a master vault directory. Its pattern-addressed vault documentation and limitations define the boundary. This does not promise forensic invisibility, deletion of historical copies, or protection against a compromised phone.
For practical decisions, start with a private-photo threat model and the comparison of separate pattern-addressed spaces. Decide whether interface compartmentalization addresses your actual problem before relying on it.