I take your opinions seriously. You offer words of caution built on years of experience. My own limited experience shows that the GM OLM works. Our 2005 Silhouette has over 100,000 miles on it and doesn’t use oil. I have changed the oil when the OLM shows less than 20% life remaining. It typically goes 7500 miles despite being used for many short runs. California tested the GM OLM in their motor pool and found that it worked so well that they use it to determine oil change interval for all their fleet. They also recommend it to everyone; I read about it on a California State web page. This was a detailed study where the state motor pool evaluated engines with and without oil changes using the OLM. Third party professionals studied it, and they found it works.
I would not categorize your skepticism as wrong, just cautious.