I've run into this too as a "driver" and a tech. I've noticed that some machines "mini levers or big levers" will allow you to say tilt back while lifting and others will not (They will allow lift OR tilt) but not both. When you say "revving the engine, how do you mean? Like 3000 rpm revs or a "touch of the pedal"? Tilt with a load does require some rpms, so that seems reasonable. Out of curiosity, are you use to an electric forklift? I was, and at first had to get used to the concept of revving the engine for hydro's.