Spectre, Miss PN experienced something like that. 1st tour, first report, and very weak reports from 1st and 2nd. She had worked very successfully on an oil spill that would have taxed someone far more experienced. She had been directed by the station commander who had good oversight of her job.
One wonders if the two junior RO benefitted on their reports.
Going back to the 50s/60s there was clear evidence of favouritism, especially as the executive cadre was almost exclusively Cranwell which was almost exclusively pilots. There were several cases where the flt lt was promoted to sqn ldr when his sponsor made wg cdr and so on up the greasy pole.