Science asks about physical patterns and behaviours in nature. Science asks how things behave. If someone asks why things are the way they are they are doing philosophy and drawing inferences from evidence. If there is intentionality in nature that wouldn't fall under the category of science. There's no method for testing if nature is exhibiting intelligence. Biology seems to use a lot of terms that I would consider to be terms that apply to intelligence; repurposing, transcription, code, functionality etc.. Physicalism, materialism, and naturalism are metaphysical positions.
I disagree. Prior to the scientific revolution, say the 19th century, in the Western tradition, all human inquiry fell under the umbrella term of Philosophy since the time of the ancient Greeks.
What changed? Those specializing in natural philosophy began to realize that one could not rely on intuition and logic in drawing sound conclusions about the questions they were investigating. They discovered that human investigators were fallible and that the scientist philosopher could not trust his/her intuition alone. As a result, principles and standards were developed in order to mitigate human error. The rest is history. Once the inherent fallibility of the human investigator was addressed, natural philosophy/science began to make great and rapid strides in expanding our understanding in those areas where this approach was applied.
A scientific approach simply means to identify and mitigate human error in the investigative process. Why would we exempt any field of inquiry from that?