I also use both DEVONthink (Pro and ToGo) to support my long-form writing with Scrivener. It never occured to me to do what you want to do, nor do i think it would be a good idea. I don’t have any proof of this, nor do I intend to test it–perhaps you can and report back?
I keep all my Scrivener projects in one macOS folder, synced with Dropbox, to enable moving them between macOS and iOS devices. Backup zip files are of course stored somewhere else. Like DEVONthink, Scrivener uses the Dropbox API to make this a pretty-much bullet-proof sync mechanism for their files. How that syncing would be possible for Scrivener packages if the files were in DEVONthink is a mystery.
Scrivener, like DEVONthink, is an app that keeps it’s files in a macOS Package with all kinds of stuff going on in the app to keep track of it all. I think of both of the apps as a sophisticated database application. How Scrivener would react to having stored inside itself all kinds of DEVONthink references is a mystery.
I rely mostly on the Scrivener “Recent” file list to open up a project as I almost always am working on one or two projects at at time and these projects always show up on the “Recent” list. I rarely go into the one folder (via Finder or File/Open inside Scrivener) to get old projects. How that “Recent” file list would work in Scrivener if the files are not in the local file system is a mystery.
You mention the DEVONthink “file hierarchy”. I don’t consider that a thing in DEVONthink. DEVONthink’s Groups are not file system folders. They are a figment of the DEVONthink designer’s imagination implemented as “Groups” and “Smart Groups” for us users.
You mention you don’t need DEVONthink’s searching and indexing. But if the Scrivener projects are put into DEVONthink, whether indexed or imported, they will be indexed and could appear in searches. But as one should not, like in DEVONthink, delve into the internal’s of the application’s database, what is the benefit?
Scrivener projects for me, eventually get done–or at least there are interim drafts/deliverables. For me usually these are PDFs. Of course I put these PDF’s into the Project group in DEVONthink where I keep writing project references, contracts, emails, … list is long. I just don’t keep the Scrivener packages there. That’s just me, which is the basis for me upon which I wonder the value of putting Scrivener packages in DEVONthink, especially with all these mysteries. 
So … does it work? Dunno. More importantly, I would not do it and instead rely on Scrivener and macOS to keep track of its projects and if these projects are to be structured in some sort of structured hierarchy, use the macOS file system with Finder which is a structured hierarchy to do so.
DEVONthink is not intended to be a macOS Finder replacement, nor is it intended to be a place to dump everything. Can it be a place a dump stuff? Yep. I have that problem sometimes.
Might work. Make some test Scrivener projects, and test.
But no matter the test results, even if it works, not something that I think has a lot of value. I accept and support that you think differently. But test, test, test.
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- reluctantly…