The basic lift formula is L = q S CL,
where q or "dynamic pressure" = 1/2 x density x velocity^2
S= wing area,
CL = normalized wing lift (normalized = reduced to the coefficient)

The only variable with altitude is q (dynamic pressure).

If L is constant, which it must be to keep the airplane at constant altitude, and the air density goes down with altitude as we know that it does, then to maintain constant lift, the airplane must go faster which it does. And it goes a LOT faster which is why high altitudes are preferred for best speed.

A jet going 260 knots "indicated" will exhibit a true airspeed in excess of 420 knots at high altitude. Higher speeds are common, transport jets often go over 500 knots true.

So is the AoA higher? No, the true airspeed is much higher.