I know that traditional classical bass technique is to always have the left hand fingers curved, never collapsed. However I've noticed that some very exceptional players occasionally collapse the knuckles, sometimes in the high register as well as elsewhere. I am wondering if their rationale is to collapse the knuckles in order to be able to place more flesh on the string than is possible with curved fingers? Or is it simply poor technique? Finally, I am wondering if there is any evidence that playing with collapsed fingers can cause physical damage to the fingers?