I’m just speculating so someone else might know better. What I think is going on is that if your monitor shows especially short-wavelength blues, since this image uses pure #0000FF blue, it’s possible that the blue is so pure and short-wavelength that the lens of your eye doesn’t focus those pixels quite right, and it ends up at a different focal plane than the other colors, especially the pure red which is very long-wavelength.

The iPhone might use less extreme wavelengths for the colors, or use LEDs that are less spectrally-pure.

Edit: like the user named Someone commented below, it looks like this phenomenon has a name - chromostereopsis.