Heya, so a friend of mine is planning on playing a Svirfneblin Alchemist (vivisectionist archtype)/Unchained Rogue who specializes in building Stone Daggers to be used in conjunction with Disposable Weapon feat and Butterfly Sting feat. For his alchemist Discovery's he was planning on getting Vestigial Arms. He believes that while these arms do not give additional standard attacks, as per the rulings on it, that they can be applicable towards additional attacks via the Multiweapon Fighting feat.
Naturally, I feel this seems a little off, as I believe that the ruling implications on it imply that said arms can be used for attacking, but does not grant additional attacks based on the number of limbs.