Old conductors trick or not?

Remember this from the Seinfeld episode entitled “The Doll”?

Kramer and Frank Costanza are in Bob Cobb’s (Maestro) Office
The Maestro doesn’t have pants on so Kramer and Frank are confused.
Maestro: Ohh, my pants. (Begins putting on a near-by pair of pants) It’s an old conductor’s trick I learned from Leonard Bernstein.

Kramer: Really

Maestro: You keep a perfect crease by not sitting in them before the performance.

Kramer: That’s good thinking!

Is this really a Leonard Bernstein thing?
Or is Bob Cobb full of it?

So you really take every line in a comedy show literally?

If you’d ever had the pleasure of meeting Leonard Bernstein, you would know that the very last thing on his mind–ever–was the crease in his pants.

You met Leonard Bernstein? What was he like in person?