Comment # 4 on bug 1017778 from Josef Reidinger

Current work-flow is that it will always write to disk which where is located
"/boot", so in your case it is /dev/sdb5 and disk is /dev/sdb. Reason is that
we do not want to be too intrusive and touch device where is no opensuse
content. So we modify disk with boot partition.

Jiri - why prevent? for me it is valid usecase. You can change boot order and
it will work. It also helps with redudancy boot feature. As it reduce critical
path ( if /dev/sda is dead we still boot ).

We no longer use BIOS boot order and keep things simplier.