The bug
If a baby turtle grows up to an adult turtle there is no scute dropping. It drops only if you kill the adult turtle right after its grow. This bug happened on a server.
Comments 2
Is this still an issue in the most recent versions (currently that is 1.16.3, or the latest pre-release 1.16.4-pre1) of Minecraft? If so, please update the affected versions and help us keeping this ticket updated from time to time. If you are the owner/reporter of this ticket, you can modify the affected version(s) yourself.
Can't confirm for 20w11a on a single-player world, can't currently test it on a server