I think they are (nominally) 588cc - but there is some discussion about that, since 3 different rotors/seals sweep the same volume, effectively you are getting 3 cylinders in the space of one. However, 588cc is what has been decided.
I beg to differ on the power subject - an engine has to have a torque curve - thats how infernal combustion engines work.
They can have good torque from idle, which is what you are describing ?
But if it had the same power at idle as at full bore...
P.S. Nearly went for a ride on an ex-police one, some years back.
But the bl^&% thing wouldn't start.
Spark plugs and 2 stroke engines, sigh.
And at 22 quid each.....