Reconsidering rescuer safety is an ongoing task. Snow that remains above the avalanche's crown, which is called "hang fire," is rarely a safety concern unless somebody skis onto it.
I have surveyed dozens of avalanche experts and have not heard of a case where rescuers were buried by a secondary avalanche while they were performing a companion rescue on the avalanche debris. I did hear of one rescue that was called off due to secondary avalanches and another where skiers who were on the hang fire triggered a secondary avalanche and were injured. There are several cases of avalanches burying professional rescuers later (often in the following days) as the snow continued to accumulate. It is also important to consider the risk of avalanches from converging drainages.
Most importantly, consider the significant risk to rescuers as they attempt to access the avalanche site and when they are returning to the frontcountry.