Magus använder arcane pool för att få vorpal

Jag läste upp på Magus-klassen och jag har några konflikter om hur Arcane Pool -funktionen används.

At 1st level, a magus can expend 1 point from his arcane pool as a swift action to grant any weapon he is holding a +1 enhancement bonus for 1 minute. For every four levels beyond 1st, the weapon gains another +1 enhancement bonus, to a maximum of +5 at 17th level. These bonuses can be added to the weapon, stacking with existing weapon enhancement to a maximum of +5. Multiple uses of this ability do not stack with themselves.

At 5th level, these bonuses can be used to add any of the following weapon properties: dancing, flaming, flaming burst, frost, icy burst, keen, shock, shocking burst, speed, or vorpal.

Adding these properties consumes an amount of bonus equal to the property’s base price modifier. These properties are added to any the weapon already has, but duplicates do not stack. If the weapon is not magical, at least a +1 enhancement bonus must be added before any other properties can be added. These bonuses and properties are decided when the arcane pool point is spent and cannot be changed until the next time the magus uses this ability. These bonuses do not function if the weapon is wielded by anyone other than the magus.

Till min läsning föreslår detta att Magus aldrig borde kunna lägga till vorpal, eftersom det är en +5-förmåga och med ett vapen som behöver +1-förbättringen, kan det bara inte fungera. Har jag missförstått något här?