He's right. If you can control the kite in all conditions, then you can kite anything even on land - like me!

With kite control you can do jumps and all the tricks that go with the kite. Back rolls should be easy once you have the kite under your power.
If you shudder at the kite and the power of the wind (note I said wind - not kite), then you are not ready for kite surfing.
Even a trainer kite is not enough IMO. You need the real deal - harness, a real kite, board, choppy water, good 20knots and practice, prac, prac, & more prac