Control reversal speed is way lower than divergence speed. It may actually lower than operating speed for some aircraft, which is why they have inboard ailerons/flapperons and/or use spoilers (that don't suffer control reversal) for roll control at high speeds.

Control reversal (at high speed; there is also control reversal at stall, which is different) occurs because the force generated by ailerons twists the wing sufficiently so that the aileron starts to act more like trim tab. For that the wing has to flex, but it does not have to flutter at all.

Spoilers act closer to the wing mid-chord, so they don't twist it much and thus don't suffer reversal. In fact they twist the wing a bit, because pre-stall lift acts more forward than post-stall lift, but this twists the wing forward and thus further reduces the lift, so still no control reversal.

Control reversal speed is way lower than divergence speed. It may actually be lower than operating speed for some aircraft, which is why they have inboard ailerons/flaperons and/or use spoilers (that don't suffer control reversal) for roll control at high speeds.

Control reversal (at high speed; there is also control reversal at stall, which is different) occurs because the force generated by ailerons twists the wing sufficiently so that the aileron starts to act more like a trim tab. For that the wing has to flex, but it does not have to flutter at all.

Spoilers act closer to the wing mid-chord, so they don't twist it much and thus don't suffer reversal. In fact they twist the wing a bit, because pre-stall lift acts more forward than post-stall lift, but this twists the wing forward and thus further reduces the lift, so still no control reversal.