I think it all depends on what breast tissue you had before (I might be wrong). Ie although I was a 34d pre op I had a lot of loose skin (saggy). So the implants have just filled out the space that was in there and my size hasn’t changed that dramatically I’m just very full now. If someone who had full 34d had the same implant size or even smaller they would appear a lot bigger because they had more to sit on top/under.
However imagine a girl who is very flat chested and has an implant stuck to their chest- they may appear bigger as they are just all implant.
I may be wrong but that’s how I’m looking at it.