At the very first moment when you visit directory.io to find the page number of your offline created private key, it will be very easy for the admin of the page to steal your funds immediately PLUS your offline generated key is not offline anymore. There is no need to repeat the visit, because the attacker (admin) can simply check all visited directory.io pages and check the balance of all private keys on that very page.
You obviously didn't read my posts! I was thinking about USING directory.io as an offline wallet generator - IF I could get the code offline. Unfortunately, the creator hasn't made the code downloadable.