The last_updated_at argument to .to_icechunk() is optional, with the default being not to set any checksum in icechunk. This means that when reading virtual chunks from the icechunk store checking that the chunks are not stale is currently opt-in.

It should be opt-out instead, as this is much safer, and there is arguably not a lot of reason to even turn this feature off. It could be implemented simply by changing the default behaviour to use the current time as the timestamp.

cc @mpiannucci