Multivalue field has wrong norm when the field value is tokenized, the field or document is boosted, and the field is not source of copyField.
In the above example, "features" is source of copyField. On the other hand, "dyn_not_copied_txt" is not so.
"features" and "dyn_not_copied_txt" have the same type attribute (type="text_general"), the same values ( ["a","b","c"] ) and the same boost. So, both fields must have the same norm in the document.
But, in boosted document only, the field that is not copied have too larger norm.