The purpose of a warm up is to increase circulation and literally raise the temps of the muscle, wake up both the metabolic and nervous systems, get the proprioceptors in the tendons ready for increased loading. I’m sure you are familiar with the felling of “flash pump” you get from inadequately warming up before getting on what might not even be a very hard climb for you. Thats the result of the aerobic metabolism in those forearm muscles not being fully on line. To get the most from your hang board routine a good warm up is essential. You can try wrist curls where you let the weight roll almost off your fingers. Also do lots of big grip hangs, hand stands and wrist mobility. Or make a small traversing wall at home with big holds to use for this purpose.
You wouldn’t think of doing any other hard strength program without a warm up, would you? They’re your tendons and ligaments, but blowing one is no fun.