So I suspect this is going to be a common answer to many questions. The simple answer is often the card mechanics the art team is given changes over time as design finds that they need to change a cards strengths, if the change is too dramatic we try to recommission the card and use the prior art for slush in a more appropriate card in a later set. But that only happens if we have the time and budget. So with The Sound of Thunder (a piece we didn’t work on, but I can lay out a theory based on our experience so far), it’s a safe bet that the original card mechanic had more to do with cavalry and less to do with battle maidens. Another example of this (mentioned on Facebook) is Moshi Nakata the card started out one way but over the course of playtest it was made into a Commander from a Thunder Shugenja.