consistency: (sub)tasks do not become inconsistent with each other if globbing for datacards changes due to new/removed files
massive speed up: instancing workflow branch tasks (e.g. in UpperLimits) would previously repeatedly resolve the datacards parameter slowing down the task-tree building & workflow starting by a factor upto 100x (depending on storage load; this was enough to bring down eos directories/nodes that contained the datacards)