It's all nice and dandy that you're so eager to tell him that there's no such thing but in fact you are wrong.
1. There is an emulator of the GBA that works in standard DS mode - it's just slow as hell and limited to circa 4Mb ROM's, making it relatively useless.
2. DS Lite and the original DS retain full GBA compatibility, provided he will purchase a SLOT-2 solution to accompany his R4i, he may enjoy full and native GBA support.