In doing some additional digging, I found this post: Dwolla and Plaid integration issues - #6 by vanmeter.developer.
I tried to move it to production on my side in Plaid to see if it fixed it, and it actually did.
In my humble opinion, this is something that should be highlighted front and center in the Dwolla documentation (i.e. its lack of true testing support with Plaid’s “development” environment). Better yet, a more informative error message (like "Plaid development tokens are not supported in production…") being returned could save developers thousands of hours (in aggregate) chasing down a solution to a problem that really doesn’t exist.
Hopefully, this helps someone else out that will likely run into this same exact problem soon enough