Hmm ... looks like I spoke too soon
The problem checker is flagging up the problem again and clicking Refresh definitely brings the message back.
I've read and re-read the code that you linked to, @zogstrip, and it certainly looks as if it should work
There are only three settings that the message complains about. One of the fields definitely has a value and, given that I've got "s3 use iam profile" checked, the other two fields shouldn't be a problem:
I can put dummy values into the access fields to clear the message but that isn't really the point