This is curious:

I'm a little confused about it though: I thought some of what distinguished Ark from something like a sidechain is that Ark follows the same rules of Bitcoin script as mainchain bitcoin.

One explanation is that this is just testnet -- which it is -- and so they are demoing what bark could look like if we had BIP 446. Anyhow, something for the people who want to do weird things with bitcoin to play around with.