Why does Notch filter have no effect?

Hi there,
I did a flight with inactive Notch filter.
After that I repeated the same flight with Notch filter activated:
INS_NOTCH_ATT 15.000000
INS_NOTCH_BW 20.000000
INS_NOTCH_FREQ 85.000000

But I see no difference in the FFT results when doing:
python mavfft_isb.py log.bin

Here are the logs:
without active Notch: www.transfernow.net/49jow8u7683d
With Notch: www.transfernow.net/73jmo9r2183c

I’m having the same issue, it seems. I flew several near-identical flights with different notch filter settings, but the FFT profiles are unchanged. For example, here’s three flights: no notch filter, notch at 100-150 Hz, and notch at 175-225 Hz.

I’m running AC 3.6.7. These flights were done with the IMU batch sampling.

Log raw IMU data(unfilter), so FFT profiles unchange