Actually, back during the height of the Pac-Man craze there was very little consensus among fans about just what certain game elements were "supposed" to be called. Those which we usually call "energizers" today were in fact sometimes referred to as "power pills" even before the 2600 port, as well as "power pellets" (that one came from the cartoon, I think), "cans of spinach" (as in Popeye), "table turners," "blinkers," or simply just "big dots." For the most part, Atari's terminology strikes me as being a way to use easily-trademarked names for things that arcade gamers had multiple names for. Although, using "wafers" as the replacement for "dots" does kind of make sense given how they appear as dashes on the 2600.
Getting back to the box art, one thing that always struck me as weird was that, unlike virtually every other picture-label 2600 game, the artwork was different on the cartridge itself than on the box. The box featured a more arcade-ish looking Pac-Man character, while the actual cartridge depicted exactly the same scene, only with a grinning yellow globe with arms and legs instead of the familiar "pizza with a missing slice." That's it, everything else was identical.