Just like the title suggests: I was just awarded the Steward badge for Close Votes & Low Quality Posts, although I already got them like 6 months ago. My guess is this is a bug, as they are meant to be awarded once for each queue.
This is not a bug; it's part of an update to the review queues. You now get one Steward badge for every 1,000 reviews in a single queue. For more details, see Steward badge can now be awarded multiple times -- backfill details on Meta Stack Exchange. The badge description will be updated shortly.