Created clips are not appearing under "Recommended", just under "All"

Same difference, recommended is still “clips the algo thinks are good” what makes a clip appear in recommended (either in the front end or the dashboard) is outside the realms of the third party developer support routes because it’s first party.

I don’t think you’d get an answer from Twitch on it either if there was a place to ask them.

It’s still algo powered.

The type of application is irrelevant it doesn’t do/change anything, it just hints to Twitch Staff what you use the ClientID and generated tokens for, but doesn’t have any mechanical functionality that changes behaviour

A clip is a clip is a clip regardless of the method used to create it.

Creating a clip via the website, calls the clip service and it makes a clip
Creating a clip via the API, calls the clip service and it makes a clip
Creating a clip streamdeck, just creates a clip via the API, calls the clip service and it makes a clip

Regardless of the entry point it all calls the internal clip service.

So why does a clip not show up in recommended, no idea, I guess the algorithm decided it wasn’t worth recommending.