I tend to agree but that depends of what is meant by "beating the game". Using again the example of platinum trophies for AAA games, I'm certain that there are a majority of people who worked on a big game who either can't or would not take the time to achieve platinum trophies. Consider trophies like "beat the game in sudden death mode". Very few players in the world are able to achieve this for most games. Of course it has been developed and tested and yes, some testers are able to do it. But you don't need hundreds of dev working on the game to have achieved platinum or got that trophy to know that 1)The trophy works and 2)The trophy is doable.
In my case I'm beating the game more and more often after extra testing hours... to the point where I think it may be quite easy when you get used to it. Originally some levels where a bit harder and there were less "extra life" and "extra boost" bricks available in the levels. But it's OK because in a way I traded the difficulty entry level for difficult trophies to try and keep the interest going. So you may have beaten the game once, but can you unlock all the trophies? Can you do it without using extra-boost meaning score extra points?
I'm about to release the web version so you'll be able to check it out more easily ;-)