I agree with the first statement. But the second statement seems odd, wouldn't the method work all the time for that following condition. A screen width can be an integer value of 580 which is always certainly greater than an arbitrary value of 20 hearts.
Yes, but what if you want more than 20 hearts later on? Or add more things (like armor, ammo indicators, which also take up screen space and reduce the amount of screen estate available for showing life)? I believe this is what was meant.