Cannot run my template in .dbt extension in Oracle 12c DBCA
For anyone facing the same problem: the reason of the error "The template data is not in the expected format" may be different interpretation of negative values between the different versions of DBCA.

Deletion of the following tags with negative values in the Testing.dbt attached by OP does the trick:

initSize
blockSize
increment
incrementPercent
minExtendsSize
minExtends
maxExtends
maxSize
uniAllocSize
id