Bit locker Encryption still running at 128kb instead of the required 256kb in task sequence.

We use SCCM and have created a Windows 10 deployment which should set Bitlocker encryption to 256KB but instead it's setting it to 128KB. The step to change the encryption is set in a build task sequence.

Its not Group policy that is affecting it as its occurring well before then and at build.

Does anyone have any suggestions what it could be?