It's debatable honestly, it depends on what you want to achieve and how you want to achieve it.

If you want a side chain that can go beyond hive limitations with things like sharding etc, you want to have peer to peer validation.

A concept where you would need it would be something where you have a side chain with its own blocks, it's own peers etc. And it only syncs it's state with the main chain now and then to benefit from its security. In that case you can have a side chain that does anything you want with like proof of work 1s blocks or whatever.