The archaeologists make three suggestions and this is just one of them. Archaeologists form hypotheses based on the available evidence but are also prepared to be wrong. It's not unreasonable to explore theories beyond what seems obvious.
this is not just a bad theory, it is also a very offensive, misogynistic bad theory.
"Price said there were other indications that the Vikings thought in less binary terms about gender than was once believed. These include laws preventing men and women from breaking gender norms in terms of dress and behaviour, which he said showed that a few people did subvert these traditions."
You might as well argue that Jim Crowe laws are evidence of a sophisticated understanding of racial identity, and that any black person who did not fit into these narrow confines was 'trans racial'.