This is probably true for most cases, but keep in mind that there are also refractive limits. My vision is between 20/30 and 20/40 (depends on the day), but it's all astigmatism which is what got me. There's a link to the medical requirements somewhere around this site, they have all the limits for refraction, phorias, etc if you are worried.
I have the same issue. When I went through NAMI (a month after having a current flight physical), I was told my eyes were so close to the limit, there's no way I could have been worse and still be w/in reqs (back then it was 20/30). After the exam, I asked how I was. They said I was worse...but still in the limits. Um, thanks. The issue was the astigmatism, which is finally starting to cause me problems 10+ years later (meaning needing glasses when I didn't used to).
There was more to the story at the time, but you get the idea. It's not as cut and dry as "20/40, you're good."