It is, but the adhesive used is aggressively strong and annoying to take out safely. And it’s so strong that you bend the battery in the process, harming it forever.

Think about that compared to a GBA: open one screw, one door comes out, battery pack can be manually removed and reused how many times you want. You can even carry an extra pack and double your battery life.

Replaceable battery packs are very different from a raw cell glued to the chassis.