With the two images, I think you’re just looking at the wrong thing – I believe the designer is talking about the actual anti-aliasing that’s going on with the bitmap scaling – How four pixels are represented as one in the smaller size, not any real changes in the size of the elements. The blurriness that comes from using the wrong scaling algorithm can be extremely annoying on smaller screens, and is what most designers are referring to when they talk about ‘pixel-perfect’ in regards to scaling..

At the end of the day, it’s not about being able to understand/do someone else’s job, it’s about having clear enough communication that you don’t have to..