It seems a bit like saying "Jack Nicholaus is an actor playing the part of a golfer," or something along those lines.
Jack Nicklaus (who I assume you're refering to) is not
an actor playing the part of a golfer. He is actually golfing.
If you are presenting "magic" in the sense of supernatural forces on display, and if you cannot actually command such forces, you are an actor playing the part of someone who can.
This is what Robert-Houdin said. It's not dogma, it's just a simple statement of truth. Unless you can really make the coin disappear, you're an actor playing someone who can.
What it means is that the techniques used by the magician to play his part are the same techniques used by actors to play theirs. It means that if you want to be a better magician, you need to work on these things.
By the way there is an entire class of magic to which this doesn't really apply. Some magicians don't really do "magic" but are more sleight-of-hand experts. In other words, the audience knows the tricks are performed with sleight-of-hand, but they are still amazed at the level of dexterity displayed. When Martin A. Nash, performs as "The Charming Cheat", sleight-of-hand is an essential part of the character.
Of course you will still have recourse to many of the tools of the actor. Or perhaps we should talk about the tools of the performer. I think even those who disagree that magicians are actors will agree that they are performers.
I am not qualified to discuss the teaching of acting techniques, but I practice several of them and they are largely responsible for any progress I make as a magician. I have worked on:
One of my best friends (and erstwhile roommate) is a broadway actor and vocal coach, and I've worked with him a lot on my voice. Plus he brought everything he learned at acting school home. It's fantastically useful.
Acting/performing techniques are the basis of
magic. I guess it's not surprising. Magic is a performing art, after all.
By the way when you first begin studying acting techniques, your performance will improve dramatically in some areas and get noticably worse in others. This often leads to the effect Mark Lewis has noted.
The good news is that if you keep working on it, this problem will go away, to be replaced with new, wonderful problems that you would never get to face otherwise.