I'm going to make an educated guess, and we'll see what comes back.
It is clear that one or more Obsidian devs have badmouthed Chris to you in confidence, and there have been a few times where it seems you are relaying their accusations. One of those I recall was something about the reason for communication breakdown due to internal grudges/mistrust.
In Eric's PM/email he also admitted he gave Chris little oversight.
Throughout the entire development there were hints in interviews, videos etc that there was a rift between Chris and (some of) the others. It seems like there may have been some passive aggressive animosity that caused a communication rift between them. On the one hand you have Chris' work which more closely resembles what we (the informed 'fans') expected from the Pillars companions, based on the Kickstarter pitch and earlier media. Chris wrote the companion guidelines for the project from memory and his design fits what he was telling us in his earlier narrative updates. You then have the rest of them which feel far more 'produced' and formulaic, more closely resembling Baldur's Gate style companions.
From what I recall, Chris may have started working on his companions earlier in development than everyone else, and his role was basically reduced to 'write these two companions' down from a bit more. The other narrative designers all had other jobs to do such as area design and writing for quests etc, and it appears Chris did not, despite having a lot of OTHER things to do. Chris is also the most experienced Narrative Designer there, and seems to be more productive at producing (quality) content.
I don't think it's too difficult to image how Chris ended up coming up with a lot more words than everyone else, and a different tone to everyone else, if he wasn't talking to the others very much and they also weren't talking to him and the manager(s) on the project weren't managing him properly.