Strawmen's got nothing to do with it; I just don't see why one should try to make a product with an unneccesarily limited set of use cases.
a) Encrypted storage would be a benefit for both Laura Poitras and just about anyone else; true.
b) Adding steganography does not put Laura Poitras at a disadvantage; however, it may provide a benefit to other users under other use cases. Also, it is not technically very difficult or even that expensive to develop.
c) To some users, the existence of encrypted, visible files could be just as bad - perhaps even worse - than unencrypted files; after all - you are basically showing the person challenging you that you've got something to hide.
So - I think adding the option of plausible deniability will add negligible complexity while making the potential user base larger, thus making a camera (or memory card) incorporating this technology more commercially viable - benefitting both the Laura Poitrases and the others. No strawman.