As I've said before. No bias involved. Naruto and his side have all of the healing feats. If Sasuke DID use preta or something similar. Why did it glow red? We've seen red Kurama cloaks heal before. We've seen preta path at work. I don't remember it glowing red or a darjer colour of whatever it was absorbing.
Naruto was enraged that Sasuke was hurt imo from what I saw. He was surprised that Sasuke healed so quickly and grabbed his arm as Naruto was going ham, wrecking Momo's attacks, king kong style.
All the evidence points towards Naruto/Kurama healing so I'm going with that until I see the full movie.