This didn’t make sense to me.
Did Allen not realize Nolan was a viltrumite? Nolan implied that he threw Allen back into space last time. Allen wasn’t suspicious about how he got whooped? It’s unlikely that he knew, and flagged it, bc why would he come back for a routine review?
And even if Allen did realize it and flagged it, it wouldn’t make sense for him to screw up Urath and Earth, given that he remembered Nolan (“you shaved your mustache!”)
I think its similar to how no one at high school notices that Eve is a superhero - if you’re not looking for it, it’s easy to miss. For Allen, he’s doing a tour of planets that are outside the bounds of the known (to them) Viltrum empire. He goes to earth, sees no Viltrum technology/architecture or signs of a hostile occupation and is greeted by a single guy who fights him in space, he’s probably just happy that he doesn’t have to break atmosphere to do his eval because he’s got other planets to get to.