Nope. Absolutely false.
Thee most efficient engine made in the world is steam.
Lets see your ICE engines develop in excess of 4 to 5 thousand HP with two cylinders.
Cant do it, and you know it.
Steam, in the configuration we are discussing (small, mobile power plants) is much less efficient, because water is a poor working fluid which is depleted as it is used to provide power.
Steam turbines, with superheated steam as a working fluid, are efficient in very large plants with access to almost unlimited water for cooling and steam replacement.