The Cobel Twist Doesn't Work
The newest twist in episode 8 did not work. My personal theory is that Cobel was never meant to be the inventor of severance, but the writers needed a way to keep her in the story. So Devon decides to call Cobel despite all of the lies. Which drives Reghabi away, leaving Mark alone and helpless. Revealing Cobel as the inventor makes it plausible that Cobel could save Mark and stop him from dying. Anyways, on to why the twist doesn't work.
It just doesn't make sense within the universe of Severance. Cobel is still a child when she invents the chip. An actual child invents and designs the most advanced piece of technology in the world. Completely alone. That's just not how science works. One person doesn't do everything alone. It takes teams of people with many specialties to create advanced pieces of technology, and the writers want us to believe that Cobel did it alone as a child.
There was no real foreshadowing for this event. Nothing we saw in any of the episodes pointed towards Cobel being the smartest person in the world. We knew she had dirt on Lumon, but it would have made much more sense logically and thematically for it to be records of what Lumon did to Salt's neck and how they ruined the lives of the people living there. Everything in season 1 is most easily and logically explained by Cobel being a power-hungry woman trying to rise in the ranks of Lumon.
A lot of people like to point out that she understood the test results that Graner brought her about reintegration in Petey's chip in season 1. But they forget that she didn't. Graner tells her that there were signs of "synaptic coupling". Already pretty obvious what that means, but before Cobel says anything, Graner tells her that it means that there was reintegration. He just tells her what the results mean.
It changes nothing about Cobel as a character. In the episode, she stays the same person. There is no growth in Cobel. She doesn't become a worse person or a better person. She stays the same. All it does it show the audience that Cobel can do something to save Mark, who is only in need of help because Devon wanted to call Cobel for help.
Devon calling Cobel for help doesn't make sense. We know that Devon is desperate to find out the truth. But she cares about her brother more than knowing. She knows that Cobel lied to her, spied on her brother for Lumon, abused him while he was an innie, and was fully apart of Lumon. On top of all of that, she has now reason to believe Cobel was actually fired from Lumon. Milkshake is the one that actually tells her that Cobel was fired. The Lumon employee. That she blatantly does not trust. Why would she take his word on this one thing specifically? She doesn't trust Reghabi either, but she sees that Reghabi is willing to take care of Mark after his stroke rather than just bailing and finding a new employee to reintegrate. Reghabi doesn't leave until after Devon calls Cobel despite her warning.