Not including the subjective but universal opinion that MTL has dominated on scoring chances, I believe there are two factors in play here that incorrectly tilt the EGF toward PHI.
1 - Leads. According to Javageek, shots while leading are higher probability chances. In a way that makes sense because the trailing team is more likely to take chances. However, breaking down shot probabilities by leading/trailing situations adds bias to the data. Good teams take leads more often than bad teams, and bad teams trail more often than good teams. When a bad team has a lead their EGF will receive an unfair boost on all shots, and vice versa for good teams that are trailing. Montreal has not had a shot on goal while leading for the entire series.
2 - Shot angle. This is not accounted for in the EGF calculation. Only distance matters, and that is a distance to the back boards - not the direct line distance to the net. Not only does the number of shots heavily favour Montreal, but I think the shot locations are on their side too.
Here are the shot charts from ESPN for all four games:
The Flyers are being rewarded in terms of EGF by taking bad angle shots from along the goal line.
Now, Gabriel Desjardins of Behindthenet fame actually plucks this shot information (see this post, which even mentions Ryder) and builds some outstanding goal probability charts. Here is the chart for 5 on 5 play.
The 5 on 4 situation chart can be found here.
Driven to the brink of insanity by the last three games, I actually went to the trouble of cutting a little pentagonal hole in a piece of paper and held it over the ESPN charts to count dangerous shots. The lines in the charts above are an approximation of my cutout.
Now for the totals.
7 - 6 in g1
14- 4 in g2
10- 5 in g3
11- 7 in g4
Shots within the pentagon are 35-16 in the 3 losses. This would be a rout if it weren't for Biron. And his big fat goalposts.