Does an Indictment charging a defendant as a principal in a sexual assault case extend a Defendant's basis of liability?

Although not reached here, it is noted that an Indictment charging a defendant as a principal is not unlawfully amended by the admission of proof and instruction to the jury that a Defendant is additionally charged with acting-in-concert to commit the same crime, nor does it impermissibly broaden a Defendant's basis of liability, as there is no legal distinction between liability as a principal or criminal culpability as an accomplice (See also People v. Duncan, supra ).