The question of whether it fills the monitor is irrelevant. The size of any printed picture is determined by the application you are using, in which there are many features (stretching etc) which can decide how large the finished picture is. Following your logic a 21" monitor would print a larger one than a 19" monitor, it doesn't make sense.
For your information I view all my d/l pics in Thumbs Plus, the best picture sorter on the market (and I've tried most of them).