The IRB makes a formal determination on whether or not a capstone project constitutes human subjects research (as defined by the federal regulations) as part of the screening process when IRB forms are submitted for review.
Detailed guidance about how the federal regulations define human subjects research and how the IRB comes to its determination is available here: https://assets.capella.edu/campus/doctoral-programs/IRB-Information-NHSR-Projects.pdf
If you or your mentor has questions about this process, contact the IRB at irb@capella.edu