An immunity is not ability accuracy modification. Consider Shuri. She can't have her ability accuracy reduced at all, meaning she has a 100% chance to place a shock on the opponent, assuming she has the charges to do so. You can try all you want, but that 100% chance to place a shock still isn't going to put one on Thing, who is immune to shock.
When something talks about ability accuracy modification, you need to consider those very specific words. Sinister doesn't lower the ability accuracy of reverse controls; he is outright immune. But bring in someone like Elektra, who reduces the opponents ability accuracy for each debuff on them. She can take out a lot of what's happening in the fight, but she will never get rid of the reverse controls because she can't reduce its chances.