Common mode inductance of a three-phase reactor
Differential VS common mode reactor: it matters how do you draw currents, since it is a three phase, then all currents you draw have the same direction, in turn this is a common mode choke as you would correctly find in the literature, catalogues, shop items,...
AFIK a choke, differential or common mode is not possible to build with 5 limb core. The extra limbs give a free path, even for sum of fluxes that would cancel out.