4-Mic Array "only" 12 bit ~65dB dynamic !? AC108 delivers 24 bit, why does the driver throw 12 bit away?

[v1tat]

I got the 4-Mic Array on a Pi Zero 2 running, with your latest 6.1 branch. I used the modifications of: JaPhoton posted here: respeaker#309 that fixed the problem, that restarting ends up sometimes of mixed channel order.
But now i record, in audacity, or arecord (S32_LE) but it ends up that only 12 bit are provided !? (audacity smallest nonzero value is 0.0004) I checked with the Osci and see that the AC108 delivers 4 Channel 24 bit, so it looks as the driver ac108.c ?? throws the lower 12 bit away ???

[codepainters]

Note, that Pi can pack only 32 bits per I2S (stereo) channel, and 2 TDM slots are inserted into single 32-bit channel slot.