It's interesting that every company claims to be "Boeing standard", but each operates completely differently.
Anyway, there is no technical reason to manually select the isolation valve open unless it is malfunctioning in the "auto" position. I'm not sure I'd want to take an aircraft with such a fault, because there's no way to tell if will lead to a complete lack of control over the valve with it being unresponsive to manual signals as well as auto signals. As long as engineers could verify that it's a sensing or signalling issue, not a valve or dc controller issue, then no problem.