Closer to 2x as long at somewhat higher heat. They also need a bit of attention to make sure they don't dry up and such.

IME they're super-delicious, but not nececelery convenient to make in small batches. Would probably do well in a slow-cooker or pressure-cooker if the amount of moisture / fat was titrated accurately.

That’s basically low-heat frying them for more than half an hour, according to the recipe?

Basically. The goal is to literally caramelize the sugars in the liquid you sweat out of the onions. This takes time and a lot of attention to prevent burning or sticking to the pan.

You can caramelize in ~15 min with a judicious pinch of baking soda. Common trick.