Nature itself is a tricky concept. Dictionaries often define it as the phenomena of the physical world to the exclusion of humans and human creations.
[Dictionary Definition of "Nature": the phenomena of the physical world collectively, including plants, animals, the landscape, and other features and products of the earth, as opposed to humans or human creations: the breathtaking beauty of nature.]
Nature as an idea implies a disengagement from the world. So, actually is one is strict with words intelligence in nature is a contradiction in terms because intelligence excludes non-humans, and nature excludes humans.
But this mainly shows that our concepts which disengage us from other species hamper our thinking.
We struggle with words when the slime mold solves the maze because our concepts dont fit the data.
It is not that nature lacks intelligence but that our own concepts do.