There is a lot to unpack. 1. It is more than a few seconds faster its closer to 20 IIRC when the tests were done. Example test you can run. Walk along, spot an object with you eyes, verify its a "legal" animal with binos, pull out your range finder find it again, range it, check dope chart, build shooting position, dial and shoot all without forgetting anything. Now with range finding binos walk along, spot object, verify and range, build position and fire.
2. As to the ballistic app. If you shoot mils and know quickdrop all you need is a range and holds. Past 600ish quick drop has some issues so you have to dial so that's where the ballistics app makes this even faster.
3. As stated above you don't "need" any of it but you will 100% be faster and more efficient. It really helps if you are still a MOA shooter as that math is a PITA and slow. Shooting Mils with quickdrop has been unequivocally proven to be the fastest most efficient method.