Yes, it works fine to store Scrivener projects in DT. Both of them use official Apple guidelines for package formats, for their own software, and both are designed to handle other file types that do so. Neither would be very good about promising file archival features if they ignored an entire swath of what valid file types are.
So in theory you could put a DEVONthink database package into a Scrivener project, and then put a Scrivener project into that database… but I really wouldn’t recommend being that crazy. 