The documentation still exists, but you can't launch it anymore.

What? Yes you can. I know because I just created a new domain today.

Interesting. Looks like you're right. I guess they changed their mind on depreciation. Six years ago at Netflix we had to move all of our SimpleDB domains to DynamoDB because they told us they were shutting down SDB. They also removed it from the console. But apparently you can still use it from the command line.

So yeah, you're right, it's still there.