Pac-Man & Galaga Dimensions' un-erasable save feature broke, many fans were upset that Namco Bandai could make such a frustrating, simple miscalculation. As it turns out, Namco Bandai made a frustrating, extremely complicated miscalculation. The publisher has recently explained its complex "save schemata," breaking down how each game included in the title is affected by the single-save function, in response to an inquiry from Shacknews.
Namco Bandai confirmed players have the option to share high scores online, but using the same cartridge in a different DS may post the scores twice. Namco Bandai didn't comment on the decision-making process behind its save schemata, but if it were to copy Capcom's response (along with its Mercenaries save function), it would say this was an attempt to preserve the game's arcade-style feel. And then it would never do it again.
Namco Bandai's explanation on how each game in Pac-Man & Galaga Dimensions is affected by the save schemata reads as follows, provided by Shacknews: