For people not knowing that feature, you can test it by using a theme created by contributors.
I like to add the following thought about this feature: people with eye problems like color blindness or else can use this feature to create a good experience of the Fediverse. I see this as a feature of accessability.
P.S. I am no native English speaker, hence my words may not be perfect, but I assure I don't want to offend someone.
@apps I don't particularly care though. As long as I can have dark colors in the app (as it seems to have already), then I'm happy.
A friendly instance about tech, apps and for having fun.