The question posed in the title concerns the explanation of a well-practised technique in ECR ion sources for increasing the output of the highest charge states of the ions of interest.For a long time the most accepted model was that of ion cooling,being a‘single-particle’effect.Two recent papers,likely inspired on earlier work,are proposing a‘collective’effect due to non-linear plasma-wave interaction,giving rise to turbulent heating.The mixing gas will in that picture reduce the heating.A few experiments are suggested to help unravel the problem of stating which effect is dominating. The question posed in the title concerns the explanation of a well-practiced technique in ECR ion sources for increasing the output of the highest charge states of the ions of interest. For a long time the most accepted model was that of ion cooling, being a ’single-particle’effect.Two recent papers, likely inspired on earlier work, are proposing a’collective’effect due to non-linear plasma-wave interaction, giving rise to turbulent heating. The mixing gas will in that picture reduce the heating .A few experiments are suggested to help unravel the problem of stating which effect is dominating.