I should point out that it makes no sense for the bar manufacturer to assign a "torque spec" to the bars. Torque is something you put onto bolts to produce tension, and of course, the bar manufacturer doesn't know what stem or even what kind of clamping system you are using (2 bolt, 4 bolt, etc.). What the bar manufacturers do instead, most probably, is attempt to design the bar to withstand clamping forces in excess of what stem clamping systems can provide; perhaps even by using published stem max torque specifications as a guide.

This is not to say you use max torque specs for stem bolts as a guide for installing handlebars; after all, what if you are using a Nitto steel stem and the max torque spec is, like 15Nm? Instead, you do what others have mentioned and use carbon assembly paste and tighten minimally until the bars don't rotate when you jump on them.