Problem: "Existing research indicates that (a) being bullied in childhood is associated with distress and symptoms of mental health problems...; (b) the consequences of childhood bullying victimisation can persist up to midlife and, in addition to mental health, can impact physical and socioeconomic outcomes."
I don't see how this research controls for the zero tolerance policies which have been in place for a long time, and which lots of research suggests serve to prolong and escalate conflict.
I have a pretty low opinion of the zero tolerance policies because they seem to primarily operate to the benefit of the bullies in this case: the bullying is not readily visible as a problem to the adults and when it is, many of them think as you do, that kids will be kids and they should work out their problems themselves. However, a fight is an immediate problem and the obvious instigator is the victim of the bullying.
Working-it-out is an effective approach for two people who want to solve an issue - an issue that they're both fairly responsible for.
But where you have one child experiencing long-term and unearned mistreatment at the hands of many peers - attempts at working-it-out are such a mismatched response that more mistreatment seems likely.
Solution: Let 'em work it out themselves.