Love the flat black look of 303 on my tires, but I am tempted to try some Optimum Protectant Plus-- much cheaper and also satisfies my urge to try something new.
It doesn't hurt to try, there won't be any side effects. I've seen a lot of people use Poorboy's Natural Look on tires (their interior dressing) for a matte look, so I don't see a reason the Optimum wouldn't work.
Optimum does make a tire dressing and dont remember it being overly glossy especially compared to those like Poorboys Bright/Bold. Einszett was another that was more matte or fresh versus glossy.