Some intellectual dishonesty going on here.
Since when did an 8:1 kill-loss ratio mean only "1 F-35 must kill 8 enemy aircraft in one mission, and be simultaneously killed by the last"?
A flight of 4 F-35s facing 4 enemy aircraft on each of 2 missions, shooting down all 8 (1 per F-35 per mission) and losing only 1 in return creates that 8:1 ratio - as LO noted.
As does 8 vs 24, with 8 enemy being shot down to 1 loss - and any of a number of other scenarios that result in an overall ratio of 8 enemy aircraft shot down by F-35s to 1 F-35 sot down by enemy aircraft.
The F-15 has an actual real-world kill-loss ratio of >100:0, after all.