I don't if @topjohnwu accepts this in the repo. Though it'd still accessible here so it's okay, i think. ?
I have the exact same problem.
$ getprop | grep vol [init.svc.vold]: [running] [ro.config.media_vol_steps]:  [vold.has_adoptable]:  [vold.post_fs_data_done]: 
do not work for me, have set to 30 steps, have always 15 Steps
#!/system/bin/sh setenforce 0