In currentOp output, the "secs_running" and "microsecs_running" field names are somewhat misleading. They are actually the number of secs/microsecs since the operation started. The connotation of "_running" is that the operation has been actively running for all of this time, but that might not be the case.

Better would be something like "(micro)secs_elapsed" or "(micro)secs_since_start".

Unfortunately straight out renaming the fields is likely to be impossible due to breaking backwards compatibility.