I'm unsure if he has a specific issue in mind, but the general problem with Corsair, Razer, etc is that they charge for their branding and will take cuts wherever possible to reduce the cost for themselves without passing it onto the consumer (Razer when they moved away from Cherry switches is a memorable example).
They also love non-standard size keys and odd bottom rows that make it hard/impossible to get keycaps for. The keyboards aren't terrible by any means, but you can probably do a little better for your money.
Looking at the one you linked, it seems cheap enough so you're probably getting your money's worth, but you're still supporting a company guilty of the things mentioned above... Woops, thought it was a little too cheap, that's not even mechanical! I would avoid it.