That's odd. Cruising boost is directly correlated with your engine's efficiency. Hx30's have a tiny exhaust side so they often make 10psi or so cruise boost and don't get great mpg's compared to the big sloppy H1C's that many 4bts came with. HX30 usually makes more power, or I should say makes power with less smoke than H1C, at the expense of efficiency.
I've had 4bts that pulled like freighttrains at 25 psi and ones that probably weren't making 200hp at 40 psi. Efficiency is a real big factor in that equation. Hence cruising boost is a fair quick and dirty assessment of the bigger picture.