What difference have you observed it make?
So the design is to burn off that oil, not because it is supposed to, but because it needs to relieve the crankcase pressure. Part of the oil is becoming aerated, and going back into the manifold which makes that dirty, and then into the combustion chamber, (and I wouldn't know if then into the exhaust as unburnt or an exhaust gas).
What it also does, is allow you to monitor your oil level. With a catch-can, you can take that oil and dump it right back into the engine, it's still good oil. With a properly working and monitored catch can, you can remove the "vanishing oil"/(unkown amount of burned off oil) from the equation. Oil is only going to leak out or burn off. If you really want to know exactly how your oil is doing, (with a catch can), you can: do a change, go run it, check your dipstick, and take a picture on your phone. Label it with the mileage and date. When it's time for the change again, dump it back in and check your level first.
I don't do it every time, but I did it the first time, (before I installed the catch can and after). Before the can, I was losing almost half a quart. After installing the can, I lose nothing. Maybe doing this once every year or few changes would be enough to keep an eye on it. I keep all my records in a large folder on my computer. If you do your own changes, and know your putting in the same amount every time, it would be easy to compare all your dipstick levels.