Yeah, moderate as a 4/5 on the scale makes no sense. Moderate has always been a significant severe threat, despite the connotation of the word, and even when they only had three categories was probably a poor choice for communicating threat level to the public. So when they forced in a category between slight and moderate they had to choose something that meant "relatively significant", which sounds more severe than "moderate". But in a perfect world this would make more sense:
Minimal (green)
Slight (yellow)
Moderate (orange)
High (red)
Extreme (magenta)
In reality this would be super confusing to everyone to make a switch, so I kinda feel like they should just refer to the color or number as a threat level.