Tac reloads - how to catch and retain that half-spent mag (?)

In regards to catching and retaining the half-spent magazine, tne technique I was taught in a class for tactical reloads is this:
After grabbing and indexing the fresh magazine with the off hand, and holding it between the middle finger and thumb while indexing it along the index finger....now place this off hand under the mag well and allow the half-spent mag to be ejected out and hit the heel of this same off hand. At that point I hook the base of the half-spent mag (which is half protruding from the mag well) bewteen the ring and pinky finger of my support hand and pull it out. At this point the half-spent mag is held by the base between my pinky and ring finger and I can shoot with it like that if I wish. IOW, with the fresh mag in place, and the half-spent mag between the pinky and ring finger of my off hand, I can shoot with a full support two-handed grip while retaining the half-spent mag all the while (kinda like holding a cigarette between the index and middle fingers, only now it is a magazine held between the pinky and ring fingers).

Of course, explaining it with words is tough, but it is lightning fast and smooth in action.

I have not seen a better technique than this, and it seems to work well for me. It is smooth and fast and easy.

My question is this: What are the inherent flaws in this technique, and what are some better techniques? I don't want to be practicing a technique only to later find out it is very flawed so then I have to relearn a completely different method.