Precisely, and in this thread we're comparing Toronto to Pittsburgh statistically and not Reimer to Fleury individually therefore GAA > SV%.
In your example given 46 saves of 50 shots is a .920 sv%, but a 4.0 GAA .. The Team in front of the goalie played poorly because it means the other team dominated the shots and the game while scoring 4 times and likely lost. Teams that give up a lot of shots against (like our Leafs do) and get out shot on a regular basis reflects on team strength defensively overall as it shows up in a higher sv% for the goalie when he does his job stopping pucks to the best of his ability.
If the Leafs only in turn fire 25 shots at the opposing goalie and he stops 23, giving up only 2 goals against he also has recorded a similar .920 sv% and a 2.0 GAA. His team won but because of the low shot count his sv% is not higher again a reflection on the Leafs team offense this time.