is enabling a DFF considered a Customization?

we have a requirement to capture additional information for requisitions and we wanted to capture it by enabling a context sensitive DFF field. I know DFF's are fields provided by Oracle for capturing additional information for a Business.  But would this be considered as a Customization? Our company policy is that we cannot add any customization's going forward because Oracle doesn't support it. is there a standard Document to support the claim that using/enabling DFF's is a customization?

Thank you.