I'd give the coach the benefit of the doubt.
Too many HS runners want to log miles even if they're LSD.
You should do some running at 5K pace, even if you don't know your 5K pace as a new runner. Maybe shoot for 21:00 5K. That's 6:45 / mile pace. Run easy for 10 mins, then run a mile at 6:45 pace, then run for 10 more minutes at an easy pace. How did it feel?
If it was too easy, wait a few days and try 6:15 pace. If it was too hard, try again at 7:15 pace. And so on.
The point is that you shouldn't just run LSD to hit a goal of 30 mpw. Throw in some race pace running.
The long run guidance is pretty universal, so the coach is by the book on that. I would just say to 'run an hour'. When you can do that comfortably, add 10 mins until you eventually get to 90 mins. Then you can pick up the pace a little, but the goal of the long run is to not run fast.