That's not quite correct, because:
1. To pick up load, you put more steam on your turbine, which puts more torque on a rotating mass, and for a fraction of time, your excess torque changes speed to affect the phase angle of the magnetic coupling of your generator to Das Grid. Mo trons flow out. When torque equals sync'd with the grid, stable at new power output. But yes, 99.999% of the time you are at grid frequency, which brings us to your first point of
2. Yes, you do care what the grid frequency is, but may not be aware why. If the grid was at 61 Hz, you have protective relaying that will open your output breaker within a couple seconds, not to mention your various mechanical overspeed devices. If the grid was 59.5 Hz, that timer is a few minutes long. Grid at <58.0 and the turbine will trip in a few seconds. Those low frequency trips are to avoid the LP turbine blade root cracking from sub-synchronous resonance. A pretty good presentation on this theme can be found at http://www.midwestreliability.org/04_standards/drafting_teams/ufls/BarryFrancisPresentation081024.pdf
3. You also care about grid voltage, and more recently the grid ops guys have to care about your switchyard voltages. To state it in nuke terms, they have to care about the offsite source to your Vital Bus. For grid operators out there, thats why you have NERC Std. NUC-001-1
I think you are splitting hairs a bit too much. You are right that I have protective relays for important motors when the frequency is not about 60 Hz. What I am saying is that I don't control grid frequency. For every day operations I do not give it any thought because it is out of my control anyway. Also notice my last sentence about the main turbine. That last sentence covers abnormal stuff. Yes I have Overspeed, BU Overspeed, and electronic overspeed devices. If those ever actuate, I will have a seriously bad day at the power house.
The Power/ Load imbalance comes in fast and can catch turbine before I get a turbine overspeed trip. What trips me is the RX trip due to a RPS actuation. Regardless of what the turbine is doing, I have 2817 MWt to put somewhere. I don't have the capacity to handle it all through my turbine bypass valves or safeties. RPS will kick in probably on high pressure first. It will catch other RPS setpoints but it is pointless to argue what setpoint hit first because the end result is the same. The RPS then causes my turbine trip. Don't confuse cause and effect. The results however are the same. I hear my safeties lift and have a pissed off plant in a transient. I will do my immediate actions the same way for either case and then work the EP.
If my plant has a turbine trip at 100%, my RX will trip on a safety system called ARTS. Same thing occurs for me, I do IA and then go to the EP. Regardless of what does it to me, I react to symtoms. If my RX trips, I will always have a turbine trip. If my turbine trips above 40% power, I will always have a RX trip. I will do the same thing regardless of what did it. This is why I don't care what casued it. No matter what situation I am in, I react to symtoms with my procedures as I was trained.
Yes I have performed offsite S.T. many times and called the system load dispatcher for info on offsite lines. I think you are reading way too much into what "I don't care" means in this context. I care about voltage and frequency on normal event free days. My priorities are to operate the RX safely and protect the health and safety of the public. I will never let generation concerns come before that. If stuff is not going right on the grid, "I don't care" means that I am carrying out actions to keep the plant safe. If I have to trip and use my onsite sources, so be it. If I am on my diesels and have no offsite power, when I get everything stabilized on my end, I will eventually get to a spot in my procedures to try and recover the offsite sources. Until these actions occur, I really don't care about the grid because I have other higher priorities.
I think it would be better if we argued about imaginary power. Do I burn more uranium when my MVARS are higher or lower? I think I burn more uranium when my MVARS are higher. I bet that will overspeed trip many pure electrical theory guys out there