I think a SOP should be used during the research phase but if not, I think it MUST be used during development. This way the engineers would be able have some sort of traceability to know that the processes used and design elements used during research to know that whatever is transferred are equivalent. For example, at my job we wanted to change the resin type used for our device casing. To do so we updated all of our documents (drawings, process documents, inspection documents, etc.) to an intermediate engineering status such that all sample material used to conduct verifications has was processed per released documents.