I think I could have been clearer in my description of what I was doing ...Quote from Random.Capital:
If you tested against out-of-sample once, it's not out-of-sample the second time.
In my outline of METHOD B, when I referred to optimizing "over the first group", I was referring to optimizing over the "in sample data", rather than to over the METHOD A dataset (i.e. the whole sample).
Does this address the point you are making?