The NXP Data Co-Processor (DCP) is a built-in hardware module for specific NXP SoCs¹ that implements a dedicated AES cryptographic engine for encryption/decryption operations. The dcp_tool reference implementation included in the repository selected the test key, regardless of its -t argument. This issue has been patched in commit 26a7.
The use of a hard-coded cryptographic key significantly increases the possibility that encrypted data may be recovered.