The FAQ is this. When you wield a two-handed wepaon, you can't make off-hand attacks, period. You could have a million hands, doesn't do jack.
What Lelomenia quoted is from a forum post, and not relevant for RAW (obviously, as it talks about intent, i.e. RAI).
Im not sure I can agree with that statement based on the FAQ, as well as knowing the Titan Mauler archetype exists with Jotungrip. They are certainly wielding two-handed weapons in 1 hand, and this is effectively doing the same thing I am, except at a larger penalty, as well as missing out on potentially an increase to strength. I would then think that the armor spikes could have been a technicality, but maybe a technicality specific towards armor spikes.
There's also this FAQ that everyone seems to have forgotten about.FAQ wrote:
Alchemist, Tentacle/Vestigial Arm: What does "extra attacks" mean for these discoveries?
It means "extra," as in "more than you would be able to make if you didn't have that discovery."
For example, if you're low-level alchemist who uses two-weapon fighting, you can normally make two attacks per round (one with each weapon). If you take the tentacle discovery, on your turn you can make
* two weapon attacks but no tentacle attack,
* a weapon attack with your left hand plus a secondary tentacle attack, or
* a weapon attack with your right hand plus a secondary tentacle attack.
At no time can you make a left hand weapon attack, a right hand weapon attack, and a tentacle attack on the same turn because the tentacle discovery says it "does not give the alchemist any extra attacks or actions per round." This language is calling out that the tentacle is not a standard natural weapon and doesn't follow the standard rules for using natural weapons (which would normally allow you to make the natural weapon attack in addition to your other attacks).
Likewise, if you instead took the vestigial arm discovery and put a weapon in that arm's hand, on your turn you can make
* a weapon attack with your left hand and one with your right hand,
* a weapon attack with your right hand and one with your vestigial arm, or
* a weapon attack with your left hand and one with your vestigial arm,
At no time can you make a left hand weapon attack, a right hand weapon attack, and a vestigial hand weapon attack on the same turn because the vestigial arm discovery says it "does not give the alchemist any extra attacks or actions per round."
The exact same restrictions would apply if your race had claws or you had some other ability to add claws to your limbs: the text of both discoveries
Currently I am in complete agreement with you with that interpretation.