Trapping air under their feathers and against their bodies is how basically all birds stay warm. Frizzles can't do that on top of having reduced feathering, increased surface area, and the curl of their feathers means cold air is able to get right up against your skin. At minimum you can expect frizzles to eat much more than non-frizzleds in chilly weather. Larger frizzles can
survive, people have proven that, but none of them are able to handle it as a non-frizzle would. That's very literally impossible. Serama are tiny so frizzles are lacking even more defense. It would be a massive stress and potentially lethal on its own, but you can basically guarantee that bird is burning a ton of food and has a suppressed immune system.
It's not a problem until it's a problem, and then it's already too late. The bird is dead. Best to go with caution, imo.
There is a difference between surviving and thriving, just because birds can survive it doesn't mean it is best or good for them. You couldn't pay me to keep a frizzle serama outdoors in the cold. Like I said, lots of different answers and those are my 2 cents.