Your right it wasn’t explicit, but it sure was the implication. I think the team at lucasfilm were reluctant to commit to any one explanation, they probably decided to stick to the clone route with the novelisation after backlash from the fans who (rightfully) also got he implication that the Palpatine that was in the film was the same one from ROTJ.
They never mention recovering a body at all, and more than one page, IIRC, mentions cloning, so I’m not sure how that’d work. The book is extremely, weirdly careful to avoid spoiling the ‘Palpatine is leading the Sith Eternal’ twist (given that it’s at the beginning of the movie, lol), only ever mentioning that the Sith Eternal are doing wack shit with sorcery and technology and that they’re lead and/or snoke was created by an ‘unseen master’.