If, by “unencrypted .json”, you are referring to the unencrypted vault export (saved in a JSON-formatted file), then no, this does not retain password histories. It does retain more information than the vault export that is saved in CSV format, however (for example, the CSV export does not include credit card or identity items, or metadata such as the type of a custom field). This is one reason why I recommended that you start by using the password-protected JSON export for your backups; the password-protected JSON export contains all the same data that the unencrypted JSON export does.
In contrast, the data.json backup method that I’ve been discussing above (described in detail here) — which is encrypted, I would like to stress once more — does retain password histories, modification dates, etc.