Would have had to have been

Swift’s testy exchange with Mueller’s attorney occasionally elicited chuckles even from the six-woman, two-man jury. She got a laugh when she said her security guard saw Mueller “lift my skirt” but someone would have had to have been underneath her to see the actual groping “and we didn’t have anyone positioned there”. (The Guardian.)

Why is the perfect infinitive "to have been" used in the verb phrase "would have had to have been" in the passage above? Would it be any difference in meaning if the infinitive "to be" was used instead there?