The featured api kind of sucks right now, because it’s not really featured streams but rather ‘people who could potentially be featured streams’
There are some post-filtering you can do to get actual featured streams (or likely featured streams somewhere), but typically filtering on request makes it easier for the client to consume, when they know only relevant data will be returned.
It’s a trade off: All your third party developers having to implement their own filtering rules (Lots of time for all developers while they learn the endpoint, figure out the filters they need, how to process it in their language, etc) or having official supported filters on twitch side (requires more time for internal development)
Arguments for both sides, and comes down to how important third party developer time is verse internal developer time, and how important you think that endpoint is (and the amount of resources required to retrieve/filter it on twitch side)