“Who’s the girl” is a repeated line. Rey talks about waiting for her parents. The flashback focuses on her being left as a child. The phrasing “but there’s someone who still could” begs the audience to question “who?”.
Johnson just worked with what he was given.
None of that points to any sort of mystery surrounding Rey’s parents. There’s a mystery surrounding Rey’s incredible power, and Rey’s abandonment is a key plot point, but those two plot threads are not the same.
Also, when Maz says “There’s someone who still could”, she explicitly says that she’s not referring to Rey’s parents, but instead to Luke. Her whole speech is basically saying “Forget your parents, your future lies with the Jedi now.” I wish that was where they left it, instead of making Rey’s entire character arc about heritage and bloodline or whatever.