Disappointing news here, after spending a while going back and forth with support they are not pursuing a fix of this issue at the time.
The best we could nail down is that randomly the email notification was linking to the proof in proofHQ vs the document on the Workfront project, and when it did there was not a "view details" link back to the project. It seemed that this only happens on upload, and that a workaround is going back to the proof workflow and sending another email notification manually to the reviewer/approver.
But support couldn't successfully/consistently replicate in their environments and say it shouldn't be an issue once they merge proof and Workfront notifications... someday Until then no solve for this one!