The very nature of the battlecruiser is to use your speed advantage to escape anything larger than itself. But then again, your last sentence applies to the entire German surface fleet, do not risk taking damage, so flee at every opportunity. Had Scharnhorst and Gneiseneau been upgunned in time for summer 1941, we could have seen Tirpitz, Bismarck, Scharnhorst and Gneisenau, along one of the Deutschland class and Prinz Eugen sail together into the Atlantic. Now that would be a real nightmare to the RN, since they only have three KGV class and (without hindsight) Hood that have the speed and protection to fight such a force.