This isn't out of loyalty to the Rebellion, but survival instinct; he realizes Skeen is a liability who would eventually kill him too.
The use of practical sets, like the real dam/garrison, adds a visceral chill and grit missing from "The Volume" productions.
The rebels hold a family hostage, showing they aren't afraid of "dirty" tactics to win. Visual & Technical Spectacle
The (like the Highland clearances) behind this arc Review: Andor, "The Eye" | Season 1, Episode 6