Ok seems to work if I use pin 1 on the power dock to connect the data line.

There may be restrictions on which pins you can use as GPIOs; this gave a hint:
https://docs.onion.io/omega2-docs/expansion-dock.html

By default, the Serial, SPI, and I2C pins implement these communication protocols and cannot be used as GPIOs. Similarly, the I2S and PWM pins are set to GPIO mode by default.

So I see on the expansion header (different pinout than the power dock) that pins 0 and 1 are associated with I2S so I used pin 1 and that was successful.

root@Omega-0B45:~# insmod w1-gpio-custom bus0=0,1,0
root@Omega-0B45:~# cd /sys/bus/w1/devices/
root@Omega-0B45:/sys/bus/w1/devices# cd 28-041671215aff/
root@Omega-0B45:/sys/devices/w1_bus_master1/28-041671215aff# cat w1_slave
47 01 4b 46 7f ff 0c 10 6c : crc=6c YES
47 01 4b 46 7f ff 0c 10 6c t=20437