I got the R4, and it starts inserted GBA (official) games just fine (game packs, not roms).
And about this funny program, :P, it works perfectly. It even works without a GBA game inserted ;) (The "GameBoy" logo appears and nothing happens)
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A somewhat recent firmware made the R4 able to tell the difference between a GBA game and a slot-2 flash cart, booting to the correct one. This program was made before that firmware update.