PowerSTEP01 Low speed optimization

I cannot see the effect of the low speed optimization.

I set speed to 1 rpm and watch the phase currents.

With these settings (these values are readbacks):

min_speed: 0x1fdf
config: 0x2c90
step_mode: 0x0007

I get significant distortion around 0 A:

To compare, with min_speed == 0 (so LSPD_OPT off):

As you can see, same distortion around 0.

KVAL_RUN at 0x0f, my motor is specified to 4 A.

What is going on? Why doesn't LSPD_OPT seem to bite? I have seen that the datasheet is a little shady about that bit, it might be that?

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