[ahnick]

Blockchains are highly distributed systems. At least the good ones are ;-). Blockchains have the ultimate uptime b/c every full node has a copy of the database that houses the state and in large blockchain networks (e.g. Bitcoin, Ethereum, Chia) there is always a node available. It's definitely possible to build other HA systems that are not blockchains, but even spending top dollar for 99.99% availability you probably can't approach the uptime of a one of these blockchain networks and especially if you are running your own infra and not doing it on a public cloud provider.

Blockchains are great for proving ownership because you can provide a signature for verification and then that can be cross-referenced to see if that same signature also owns the on-chain data.

There is no getting around the fact that the government chooses the system of record and property owners have to abide that choice. If the government though chose to use a blockchain as the system of record (for all the benefits I listed previously), then you don't need to worry about other blockchains, because that's not the one the government cares about.