OK, a shard reveals some metadata but still nothing about what it encrypts and this is the main point and what differentiates it from simple partitioning of a secret. I get your point though.

I took a brief look at the documentation about Shamir Backup of Keystone. The documentation merely describes what it is and how to set it up, but I couldn't figure out e.g. if it is compatible with the shards that new Trezor Safe devices create (I doubt it). As mentioned my main concern is interoperability.