Is an attraction to studying the philosophy of biology a good reason to pursue grad studies in the field?
In my opinion, yes and bioethics is a very interesting domain.
 First, there is a growing interest in ethics (which is a branch of philosophy) in the fast-growing field of synthetic biology ("next-generation" genetic engineering, the design of new organisms, genetic manipulations in humans etc.). In many publications (check out "synthetic biology" and "ethics" on google) and conferences, people are saying how far behind is bioethics, compared to synthetic biology. There are many burning questions such as: If we create new organisms, should we release them to the environment? Should we edit the human genome? To what extent? (Just curing illness, or maybe also to improve traits?) Should this ability be democratized?
Should a person's genetic information be used when looking for a job? Insurance? And so many more questions, not to mention the bioethics of the state healthcare (compulsory vaccinations etc.) 
There are a lot of scientists that know nothing about philosophy and a lot of philosophy experts that know nothing about science. There are not enough people who know both and can help with these question.