Was Rodin a coward for not fighting against Homunculus in late game?

Irrc, Kamiya said Rodin doesn't interfere with human realm affairs, But Rodin said homunculus threat could be a threat to the trinity?

The setting seems to inconsistent to me.

My 3 guessings:

1. Maybe Rodin was formally from Paradiso so Singularity found a way to suppress his power?

2.Maybe Rodin has a mutual goal with Singularity, so he decides not time meddle?

3. Another unknown entity that orders Rodin to stay out of this?