I think the confusion is because “metadata” is a somewhat loaded term here.
You can attach SSDs to existing pools (members of the same pool, but only holding that pool’s metadata) and in your case you’ve created a pool that itself is named metadata so … people might be getting a little puzzled trying to sort it out. 
Anyways.
Can you do zdb -l /dev/sdb2 (that’s a lowercase L) and post the results inside a code tag here?