That’s kind of a weird answer (didn’t he get a chance to proof it?). It looks to me like Sibelius output, so if the publisher doesn’t have the maestro harp engraver font, that would explain it. Still, doesn’t say much for the publisher that nobody questioned that!
Anyway, I’m glad you got an answer. FWIW, the composer is right–those characters in Engraver would create a standard pedal diagram.