The reason why Seymour probably comes across as being 'fake smart' or not as intelligent as he's supposed to be is because of how Eva seems to perceive his intelligence as '10', and the fact that he's supposed to understand philosophy. The problem is, if you're really going to write a character who is that intelligent and philosophical to boot, you can't just have a passing knowledge of philosophy and think it will suffice. That's like that time when Paris Hilton went to jail for one night, 'read' the bible for the first time because it happened to be the only thing in her cell, then came out the next morning saying she'd 'read it all' and was an enlightened Christian. Understanding philosophy isn't the work of a single book - a single book is a brief introduction. People who think they understand philosophy at that stage and decide they want to talk about it generally come out sounding more like a pretentious hipster rather then wise and enlightened.
I mean, considering Seymour is meant to be a fan of philosophy, and considering his age of 50-something, I think it's reasonable to assume he'll have read and reflected and conversed with other lovers of philosophy over a lot of material over the years. Probably using it for his own ends, and shaping his personality and beliefs with it bit by bit as he went. To write someone who understands philosophy as well as Seymour is supposedly meant to would take a lot of study and inner-reflection by the writer. It takes time to truly grasp.
The other mistake is giving Seymour a 10 in charisma. Yes, it may seem like 'just a character card' and largely irrelevant, but it's a bit more then that - it's an indication of how Eva envisions the character, regardless of what we as readers/players have experienced so far. Let me put it this way: Leonardo Da Vinci is considered by many to be the greatest mind that ever lived (even to this day), and even LDV wouldn't be a 10, because 10 is supposed to be the pinnacle of perfection, and he was still learning when he died.
Even though we're still to see a fleshed-out Seymour, he wouldn't be a 10 in any skill. Well, maybe in lust if he's willing to take it as good as he gives - literally - and nothing is off the table. Like, we're talking kinkiest man that ever lived here. But the fact is, nobody is a 10.
There's a sort of unwritten rule in the world of writing: don't write a character that is [supposed to be] more intelligent then you are. Why? because the character will never feel truly authentic. The fact is, we can't comfortably conceive/write of intelligence above what we possess ourselves as the writer - anyone with more intelligence would read it and instantly see the flaws and write it off, and we as the writer would lack the context of greater intelligence to see those flaws ourselves beforehand (unless someone points it out and we're not adverse to constructive criticism and extensive re-writes).
And yes, in the world of writing, some love to challenge rules; people still write character who are more intelligent then they are, and it's not impossible to do a decent job of it, but the ones who are believable are those that written indirectly. Hinting at intelligence -- observing the effects of the character's intelligence, or hearing it from a third party, for example -- rather then spelling it out directly through the intelligent character's words and actions. Unfortunately that's pretty much impossible to do here considering Seymour is a main character, and considering it's highly unlikely Eva would change the character even if she knew people weren't sold on it. The 'fake smart' thing is something people will just have to try to overlook.
I just live in hope that Eva will flesh out Seymour as she goes, and go a way to making him feel more authentic in whatever direction she plans to take him.