I'll admit that I have had some awful games with Ezreal. But seeing as we're talking about getting a particular score once, it really only helps to compare the best performances; the A+ games.
By the way, I just got an S- and it was a mediocre game for me. In games where I carried, literally carried, as in my team was losing until I pushed the other team down (Yi style) I got an A+. In my one and only S game, Xin and Malphite carried and I simply rode the wave.
Also, I agree with your assessment of Ezreal. He feels safe. I picked him up the day he was released. Item changes and rune changes affect him tremendously. I use to play him ranked and I have just returned from a 3 year hiatus so I had to rediscover how to get damage out of him. Once upon a time, building IE/PD/BT was a solid choice for him.
There are definitely champs I am much better with than Ezreal. Even before my hiatus, there were probably a dozen champs I could carry better with than Ezreal. But since my return, many of those champs are completely unrecognizable. Ezreal remains the same. Hence the feeling of safety.
Fun fact; I have been playing Ezreal in every lane this week: Top, Mid, Jungle, Support. Heh.
Top Ezreal Players on OP.GG have a lower KDA than me
Exhibit A