"Truth" of course is a red herring. "Claim" is better. And, "digitally signed claim" is better yet. Then to answer your Q: a good sharding approach should let

"Truth" of course is a red herring. "Claim" is better. And, "digitally signed claim" is better yet. Then to answer your Q: a good sharding approach should let you see all digitally signed claims (including when those claims were made) with probability --> 1.0. I'm framing this probabilistically because many sharding approaches rely on that definition. (And even non-sharded blockchains like Bitcoin itself.)