Fine. It seems inconsistent with the string bounds serialisation we already do but I don't want to drag this out. Your argument seems reasonable, but taking this approach we should have test coverage for this ```bounds=None``` behaviour so we can see when we change it in the future. An ```assertIsNone(agg.coord("weird_name").bounds)``` at the end of https://github.com/bblay/iris/blob/955c4cb9ceba3c30a867ce538d88eb63d63023ae/lib/iris/tests/test_aggregate_by.py#L502 should do it.