I make caramelised onions for work in a professional kitchen and trust me, if the owner of the establishment could reduce the cooking time (and man-hours) required for caramelizing onions down to 15 minutes, he'd force us. He's read these internet articles and tried to get the chef's to do that, and then tried to do it personally. We went back to the old method. This man has us pre-cook burger patties in preparation for lunch, and even he knows it takes longer than 15 mins to caramelise onions (well, now anyway). It tastes sweet and mildly onion-y.

We also prep browned onions, which similar to what you describe. Tastes different. It's a different thing.

Like, risotto and paella are similar but you can't just use them interchangeably.