No its not. There's all sorts of stuff you can do with capabilities that are really awkward to even think about with users. Like, when a database starts, you can hand it the capabilities it needs to access a specific directory, listen on a specific port and append (but not read) a specific log file.

User based security is usually done by the folder being owned by the database, or an ACL or something. But with capabilities, you don't need to make a database user or set any flags on the folder, or make sure the database's configuration matches the filesystem permissions. The capability is basically a pre baked file handle that can be used directly. And capabilities can do lots more stuff! They can be more fine grained - eg, "Whatsapp can only access these specific photos in my camera roll". And a program can pass a subset of its capabilities to a child process.