פירוש על קידושין 103:8

This story was used by Abaye to prove that kiddushin that cannot be followed by intercourse are kiddushin. Abaye said that in the story the sisters are not betrothed because he married both at the same time. Had he married one then become mixed up as to which one he married, they both would have both been doubtfully betrothed even though he could not have intercourse with her.
Rava said that the mishnah refers to a case where he married only one but did not say which one. This proves that kiddushin that cannot be followed by intercourse are kiddushin.
Rav did not want to learn anything about this topic from the mishnah because he was not sure whether to read it like Abaye or Rava.
I should note that this is obviously not a chronological way of understanding Rav. Rav could not have known about the debate between Rava and Abaye, for they lived three generations after he did. Indeed, the reason that Rav does not learn anything about kiddushin that cannot be followed by intercourse from the mishnah is that this topic had not yet been brought up. It is also worth noting that this is a highly abstract concept, whereas the halakhot Rav did learn are far more practical. This is emblematic of the differences between early amoraim like Rav and later amoraim like Abaye and Rava. Rav is interested in real halakhic rules, whereas Abaye and Rava are interested in abstract halakhic conceptsץ