Hola Ned

Yes, "le" is often used instead of "lo" as a direct object pronoun. It is indeed accepted by RAE in this case as it is referring to "him" (singular masculine), however, I added a hint instructing to use the "direct object pronoun" so we maintain the general rule for direct object pronouns and indirect object pronouns. I hope it's clear with the hint now that we want "lo" there, not any variation. 

Saludos cordiales

Inma