I’m not going to get into a flame war over this, but there are very many examples of overclocks on i7 systems that are stable with HT on and pass Prime95, contrary to what you say, though these overclocks are not as high as you could get with HT off. But for Cubase HT must be on for maximum efficiency, but this does not rule out overclocking.
Turbo on is more problematic for audio with X58 systems. With Sandybridge it’s mixed, apparently 2600k is good with turbo on.
The main issue is stability and temperature vs noise and a good overclock has to pass Prime95 and a few others as well, that goes without saying. It has to be STABLE even if it’s overclocked and they are not mutually exclusive words.
Though that said I imagine Steinberg would advise against it, but hopefully without treating adults like children.