This statement is underdefined for me for a number of reasons: (i) what types and complexity of work is considered, (ii) what does rigor mean in this specific context, (iii) how to interpret the adverb 'eventually' here, and (iv) who is supposed to reach understanding, what level of it, and based on what body of knowledge.
The type of work is dissertations and theses (primarily falsifiable ones and or survival heuristics). Rigor means empirically correct. Eventually means once the Lindy Effect demonstrates the work has anti-aged. The general public is supposed to reach understanding that exhibits the work’s influence. Particularly based on the Lindy Effect of the imperishable anti-aging while the perishable aging. Meaning, heuristically, the longer an imperishable has existed, the longer it will continue to.
Thank you for the conceptual details provided. I think we are still not in the position to formulate proper answer to your interesting original question. The issue is: How can a Ph.D. dissertation (apart from the national and institutional deviations) be "rigorous enough"? We, first of all, must see the two typical (internationally respected) expectations from the Candidate: (i)to show the competence to conduct independent research, and (ii) to provide evidence for the capability to contribute to the knowledge existing in one or more domains of a discipline (or disciplines). Are these a matter of rigour (or rather of performance)?
And, of course, the concept of understanding is still floating in the air... But I am sure you agree with the above. Or, am I wrong?