I am curious as to where you are getting information that the CFP is not accounting for unusable fuel.
Unusable fuel is exactly that, unusable and is not, by certification standard on FAR 25 aircraft to be displayed on the fuel quantity indicators. The exact process for determining the unusable fuel is not perfect, but also defined.
The CFP in all the flight planning systems I have looked at does not in any way consider unusable fuel and plans for Final Reserve to be usable fuel. So if you land with Final Reserve in theory it is all usable. In practice we can all accept that 100% of fuel on an aircraft is not usable and no prudent pilot would ever assume that you can take the quantity all the way to zero.