Utter BS.
There are certain cut combinations which are avoided to ensure the key doesn't get stuck in the lock though... but not that many and there are more key patterns than 6. If you want to ensure someone's not going to be getting in your car with their key, then get the lock rebuilt and have the wafers arraigned so they're aggressive, such as the patterns typically avoided. Granted, the lock won't last as long.
Hasn't all this been covered about 10,000 times on here? Why do we need a new thread about it anyway?
EDIT: Oh and before anyone says it, there is no Toyota Universal/Master key. There are certain cut combinations which rely on worn locks and averaged cuts based on the possible cuts (so you're likely to get in with one or the other if you the lock's worn enough or possibly with a little rake action), but there's no such thing as a universal.