Because your TikTok developer app hasn't been audited yet. TikTok's rule is that unaudited apps can publish only private posts, or to a small group of test users. Submit the app for audit in the TikTok for Developers portal to publish publicly.
TikTok connects through your own TikTok for Developers app, with the
user.info.basicandvideo.publishscopes; one-click isn't available.The agent posts photo carousels and videos.
The connected account appears under its display name, not its @handle.
More: connecting integrations and TikTok integration.