First, these 2 Upanishads were not composed by Yajnavalka and Aitareya. The Upanishads are the revealed word of God. They were revealed by God to certain sages who then recorded them. There may be stories in the Vedas (and Upanishads) that do not have to be taken literally, it is what they are meant to teach isus that is important. The Vedas are the only scriptures in the world that were not composed by humans.
Both Swami Gambhirananda's translation with Shankaracarya's commentary and Swami Nikhilananda's translation and commentary both show the reference to Vamadeva. The following should be noted:
The Aitareya verse is clearly not Indra. The reason it says 'while lying in the womb, I came to know' means that he has come to know this as a result of meditation in many previous births. The verse is meant to show what has come to Vamadeva - an individual jiva - through Self-Knowledge, because the Knowledge alluded to can only have come through previous births. Indra, although a deva, is only a deva for the current cycle and will be subject to rebirth at the end of the cycle. Indra does not have Self-Knowledge. Devas cannot attain to Knowledge of Brahman in their birth as a deva. Only human birth can.
It should also be noted that the chapter ends with Vamadeva and the first verse of the next chapter starts out with again a reference to Vamadeva.
The reference to Vamadeva in the Brihadaranyaka is again, a reference to what an individual jiva can attain to. So it makes perfect sense that it would have a human name and not a deva name as an example of one who has realized the Self.
Finally, I am very wary of any supposed interpretations or commentaries by Western Sanskrit scholars. They learn their Sanskrit from other Westerners and are Christian or Atheists in their own philosophies and have their own agendas in their translations. Most see Vedanta as a polytheistic religion and see the religious texts as mythology to be interpreted as such.