Comment # 9 on bug 1102569 from Mircea Kitsune

Kernel 4.19.11 from snapshot 20181224. Without the boot parameter
/sys/block/sdb/queue/scheduler still reports the old scheduler. The link
Johannes Thumshirn posted indicates the kernel should be updated by now:

Updated at: 2019-01-02 14:14:02 +0000

I'll test again once Kernel 4.20.0 is in.