The Warp 13 from TNG:AGT was confirmed by the writers to mean a recalibration of the warp scale. Going Warp 9.99995 would be too cumbersome and prone to error.
Let's summarize:
On a ship with limited supplies in the middle of nowhere cut off from its native civilization a team consisting of no scientists comes up with a way to make a paradox real. Making this paradox real results in people turning into lizards, described as a form of evolution though natural selection plays no part as it is a metamorphosis rather than a genetic change in offspring. Then a computer program fixes the problem by injecting anti-protons, which magically doesn't result in a matter/anti-matter reaction (which would cause an enourmous explosion) but instead results in a metamorphosis back to the original form.
The team:
The team that invented this technology consisted of a pilot who was in prison for the last few years, an engineer who has been fighting as an insurgent for the last few years, and a helmsman who has less personality than a potted plant, with inspiration from Nellix. None of these people are experts in warp theory. B'Elanna is the only one remotely beleivebly capable of advancing warp theory, but even so, her job isn't to invent the next big thing, its to keep a machine working. She hasn't been trained in research, she isn't up to date on the latest information, and the ship doesn't have the facilities of a research instituition. In real-world terms would the person in charge of maintaince on a nuclear reactor be likely to be the person to invent reliable fusion power? No. Starfleet probably has hundreds of people working on a way to increase propultion technology. People smarter, better trained, better equipped, and better situated to invent such technology than our klingon.
The Technology: Infinite Speed. Wow. Next you'll tell me you found the answer to x=x+7,solve for x. It's meaningless. Completely meaningless.
The Lizardification: After this it goes from sheer stupidity to something more in resemblance with an acid trip. I don't really see the corrolation between infinite velocity and DNA being fucked with. But hey, infinite velocity is a paradox, so why not throw all logic out the airlock?