answered elsewhere, but here's the solution for future generations:
take a look at the definition of PF_ADD_CHECKBOX.
you can see it's copying the passed default over the passed value.
i don't recommend changing the AE headers because updating the SDK would undo the change. (and it's generally bad practice)
just just copy the macro code to your files and fix it there, ot don't use the macro at all and define the param the old fashioned way. (which is the way the macro does it)