The HP turbine doesn't have variable output? I didn't know that. Hmm...does that mean it either runs at full power or not at all? What do you need the turbine dynamometer for then?
Anyway, depending on how much I'll get into fission reactors I might run a smaller one here or there. I would accept a 20% loss if I had crippling technical issues.
I asked once what the t-dynamometer was for, and I totally forget the answer. Automation maybe?
Its output is steady, other than spin-up and spin-down. I guess that probably means you're right, its either happy or not (you're either supplying it with sufficient steam or not)
Between that and the lack of steam block updates, its a wondrous thing to behold.