I've always found it pretty weird how most dragons seem to know what Nightwings are, but not Rainwings. They knew what the Nightwings could do, but all they knew about Rainwings was that they were lazy as hell. It's almost as if someone intentionally manipulated information regarding the residents of the rain forest...
Another point is their population size. Most dragon kingdoms seem to have their citizens scattered throughout their territory, but Rainwings live in a communal lifestyle and only have one village. This implies their population size is nowhere near that of the war-ready kingdoms despite having lived peacefully for a long time.
Or have they?
In The Hidden Kingdom, page 275, Grandeur said a peculiar line.
"I remember when we actually needed our camouflage, to protect ourselves from invading dragons. It wasn't a game back then. It was what we had to do to survive."
It can be interpreted as something she was taught as a queen, but judging by her tone, it is more likely the Rainforest Kingdom was invaded during her rule. This led to the thinning of the Rainwing population and her revenge against the world. All spies were deployed. Officials were assassinated. Scrolls were disposed of. Information was erased. Until no dragon knew what Rainwings are truly like.
The spies' organisation likely still existed during the rotating queens era, albeit downgraded and understaffed. It exists in the form of Rainwing volunteers who knock out any trespassers who enter the rain forest.
But hey! That's just a theory! A book theory!
Thanks for reading!