Most packages of ready noodles contain the information not to reheat them, for example: https://groceries.asda.com/product/noodles/asda-straight-to-wok-noodles/910002208900. It's safe to reheat rice, pasta etc., so I'm confused why reheating wok noodles would be different.
The "do not reheat" is standard text on food that's already cooked (like these noodles) with the expectation you'll cook it again. So they expect you to reheat once by stir-frying, then not again. You don't need to heat them before adding to a wok, but that's not what they're referring to.
The reasoning is usually about total time at temperatures ideal for bacteria to grow - if food is cooked, cooled, heated, cooled and heated again the total can get close to the limits. I routinely ignore that text on the basis that I cool my leftovers quickly (and reheat them quickly from chilled), but I can't really recommend you do the same. It's not just that they're covering themselves against other people's behaviour, but there is an element of that.