I’m still not quite sure what your goal is: one of TrainerRoad’s crown jewels is its database, based on which they can develop their training. It is correct that not publishing peer reviewed studies means there is no definitive publicly available evidence that the ramp test correlates well with other methods to measure your FTP or lactate threshold. Nevertheless, I have no doubt that TR’s approach is data driven, it is just that their data is proprietary. In my experience, the ramp test works quite well to my scale workouts appropriately — which is the ultimate purpose at the end.
Even if TrainerRoad did release its data (without compromising their users’s privacy), you would have to discuss the quality of the data. The ramp test is way easier to do for beginners than a 20-minute FTP test, which as far as I know is the old-school gold standard.
Moreover, even if you get an accurate measurement of your FTP, for a proper analysis of your abilities you’d need to assess other characteristic quantities such as VO2max power, sprint power, 5-minute power, etc.
So if your VO2max power is not 120 % of your FTP (which is the basis used in most workouts), but, say, 125 %, then you’d leave something on the table in workouts.
Put another way, TR is not as good as a pro-level coach who assesses you regularly and prescribes tailor-made workouts. TR’s purpose is to give you 90+ % for a fraction of the price. (Great coaches don’t scale.) Lastly, not even coaches always or solely rely on science, experience plays a huge role for them. One team mate of mine, who upgraded from the lowest to the highest amateur category within one season, has a coach. He doesn’t even seem to know his FTP, yet, races successfully. I’m not advocating for this approach, but there seems to be more to it than FTP tests.