or even hangboard.[/edit]
There seem to be a consensus that beginner climbers should not do specific training of the muscle-tendon units that control the hand and fingers. More specifically beginners are advised to stay away from hangboards, to lower the risk of injury.
Often beginners are told that if they do specific training for finger strength, their muscles will rapidly become stronger than their tendons and then they get injured. As far as I understand, this explanation is completely bonkers and contradict a century of research in sport physiology. Study after study shows that one of the main advantages of complementary strength training in sport is that it lowers the risk of injury as tendons get stiffer and stronger, muscles become better conditioned and coordination improves.
Assuming that it is true that beginners should not hangboard, and given the strong consensus among coaches I think this is a fair assumption.
I can see two models that better explain why they would run risk to injury
1. General explanation. Beginners add hangboarding to their training quite suddenly without removing time spent climbing. Often by following a program that prescribes 3 sessions a week of fingerboarding, there by going from 2-3 sessions per week of training that loads the fingers to 5-6 sessions per week. It is well known that the most common cause of injuries from sport is a sudden increase in load or volume.
2. Climbing specific explanation. Beginners are extremely uncoordinated when climbing and prone to foot slips from the most absurdly stable positions. If they have but jugs in their hands, well they would rather injure the shoulders than the fingers when they find themselves dangling from hold, holding on for dear life (as they are beginners they have not yet learned to let go and take the safe fall when necessary). If they have quickly gotten strong in the fingers they might have a small pocket or crimp in their hand when the foot hilariously pops and they injure their fingers before their shoulders.
(Anecdotical evidence: my only finger injury was in 1998 or 1999 and could be described exactly like this. I had relatively strong fingers and managed to hold on to a drilled pocket with one hand when my foot slipped. Complete with the crack of something breaking in the hand. At the time I had no idea what that sound could be.)
Explanation 2, if correct — which is a big if, would cover why beginners are better off improving finger strength just by climbing rather than improving their finger strength off the wall.
I feel that explanation 1 is more likely to be better than 2 for most injuries. This feeling is backed up by absolutely nothing at the moment.