Let's recall the basics for a bit before jumping on to the conclusions. The Shichibukai system exists to help the Marines counter-balance the Yonko. What that means is that if the new technology is deemed worthy of replacing the Warlords then it means the marines think that this new technology can help them counter-balance the Yonko which ultimately puts the Yonko under the same light as the Shichibukai. So try to come out of the illusion that this new development somehow dehypes only the Shichibukai.
It was likely a mistranslation.
Then do it yourself