Apple says they adjust the active noise cancellation 200 times a second.
We can't tell exactly what that means just from reading it, but it could very well mean that while the filter is updated 200 times a second, it isn't limited to filtering 200 Hz sound.
There are very few parameters that make sense to update 200 times a second if not the actual voltage level to subtract. If you adjusted EQ parameters 200 times a second you'd just be injecting a ton of noise in the center of the audible band due to phase jumps.
Edit: There is reason to believe it is just 200 Hz ANC. It's the same wording used in Beats over ear headphones that have a W1 chip and ANC. Those headphones have abysmal ANC that doesn't do anything above 500 Hz (aside from adding in some noise).
We can't tell exactly what that means just from reading it, but it could very well mean that while the filter is updated 200 times a second, it isn't limited to filtering 200 Hz sound.
I'd be rather surprised if it was.