In the Ruy Lopez, Morphy Defense Main Line,
[FEN ""] 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7
after 4.Ba4, the engine suggests Be7 as one of the best moves, tied with Nf6. The opening book Perfect2021 confirms this. Yet, there's no mention of this move order in any of the materials I've read so far, including the Wikipedia article and the Chess Opening Theory Wikibook chapter on the Morphy Defense. Lichess' Masters Database has only 132 games where 4...Be7 was played, out of 88,219 (0.15%). What am I missing? Why does no one play Be7 first?