For any airspeed, the angle of attack is higher with the speedbrakes up.
it will help to remember that aoa = the difference between where an airplane is going and where it appears to be going...so use of speed brakes to slow the plane means a higher aoa with decreased airspeed --or an steeper decent path.... both conditions perturb the flight path in such a way as to increase the effective angle of attack ---or if fuselage attachment angle is accounted for incidence...
