I distinctly remember this at the time. I just played all my games with no sound, a mild frustration at best as it was the only real option as a kid if you wanted to play games at night without goofy adapters for your GBA!

It's more akin to the iPhone 1 not including a jack then adding one later than the iPhone 7 removing it.

Another note: Original Gameboy games stuck way out the back. The GBA SP sure made a lot of sacrifices, and odd design choices but the fact that it fixed the biggest issue means a lot for it.