Arguably, it's not the same as P doesn't take on the F sound unless H is also there; G can have a soft pronunciation all on its own. There's no inherent illogic in the acronym, on its own.

People are going to pronounce things as they want to pronounce things, in the end, but (for the creator of the comic) to argue that GIF and JPEG (in this particular scenario) to be equivalent is of shallow consistency (but maybe that's because the general counterargument I hear most often is something along the lines of, "That's not the sound that G makes").