It is possible to explain based on the Mefarshim who say that Eliezer is Og (Pirkei d'Rebbi Eliezer 16), who was present at the Teivah and survived and would naturally have been curious about what went on in the Teivah. The Maharsha understands that Eliezer is querying why Noach did not exit the Teivah with his wife (as he is mentioned with his sons and not his wife) to which Shem responds that due to the difficulties in the Teivah they did not exit as the animals did.

As for the second story, we recollect that Malkitzedek who greeted the victorious Avraham is identified by Chazal as Shem and he would therefore be curious about the battle. He also says, "Blessed is G-d who delivered your enemies into your hands," using the term "Migen," which implies that he was amazed at the way they were handed into his hands, so the Midrash has some textual basis.

Yoel Domb