No, not really. You're just assuming they're going to continue displaying your posts on bsky.app. Everyone is reading your posts through bsky.app and it doesn't matter if your post is technically available through a side channel if it's not available through the main channel.
bsky.app is the way that people view bluesky posts. That is a fact and it will continue to be the fact for the useful lifetime of bluesky. If bsky.app dies, so does bluesky because it is bsky.app.
If the promise is: when using the AT Protocol you have control over your own data, then this is self-guaranteeing, since it is a part of the spec that you can self host a PDS.
The promise that Bluesky will always be compliant with the spec, or that the spec won’t ever change to disallow this isn’t self-guaranteeing, but you could say something similar about any of these self guaranteeing promises. For example the promise that Obsidian will always use markdown isn’t self-guaranteeing.
> The promise that Obsidian will always use markdown isn’t self-guaranteeing.
True, but Obsidian doesn't make that promise. The promise is "file over app": you control the files you create. In this way the promise is not reversible, and self-verifiable.
"...will always use markdown" is not something any app can guarantee. At best an open source app can guarantee it for a specific version (assuming it doesn't require a connection, or the user can self-host the server).