A test of 2/5 vs 4/5 seems to be an obviously invalid experiment.
The practical example of not liking the sentence is not great in my opinion. Instead of just re-rolling the answer, why not continue in that thread and say what you don't like? Or request 20 alternatives, say which go in the right direction and request 20 more? Retrying from scratch with one sample is a waste of time and doesn't indicate anything about quality.
Basically, it's all theoretical - show us the actual benchmarks/samples where the quality is consistently degraded.