The present Boolean operation implements the Cut. I suggest to implement the EXOR as follow : to exclude the union from the result.

it produces the following :

//+

Disk(1) = {0, 0, 1, 0.25, 0.25};

Disk(2) = {0.1, 0, 1, 0.25, 0.25};

//BooleanEXOR{ Surface{1}; Delete; }{ Surface{2}; Delete; }