I have been wondering how having these type of devil fruits can give us more clues on where/how devil fruits are made. First we have their origin: manufactured or from nature.
I think regarding the second option is where all the confusion start to kick, what is natural? On the other hand, if we consider the type of change the fruit gives you, this could be better accepted. For example:
Imagine we have two lighting fruits. One allows you to produce lighting, the other allows you to become lighting. With this in mind, if we consider that the fruit types dictate what sort of manipulation you achieve, then it's okay~ for Mochi to be a logia because instead of meaning that it occurs in nature, the user becomes of that ~nature~. However this borderlines with the idea of: Is Luffy's fruit a paramecia or logia?
Anyways I was just trying to come up with something.
On the other hand, if the fruits were manufactured, then it sort of clues in that, whomever made them, started to see to what extent their technology(making devil fruits) could work. So they mixed in what they could. This however brings other problems as well like: How do you produce darkness in a way it can be registered for the process. Light, magma, ice, mud, rubber. Most of them work, but I wonder, if this route is taken, how will Oda portray the creation of the darkness fruit. It is not entirely out there considering Vegapunk and Ceasar made their own versions and we know Vegapunk has had setbacks regarding the current technology of the world being outdated compared to his visions.