Solution
This behaviour is expected due to differences in file formatting between the Semiconductor Test Library API and the Digital Pattern Editor (DPE).
The API functions SaveTDROffsetsToFile and LoadTDROffsetsFromFile are designed strictly as a complementary pair. LoadTDROffsetsFromFile expects a specific, custom file structure generated exclusively by SaveTDROffsetsToFile. The Semiconductor Test Library API does not feature built-in methods to save or load TDR offsets in a standardised format natively compatible with DPE. Consequently, DPE cannot directly consume the custom file format generated by these API calls.
To successfully utilise these TDR offsets within DPE, you must develop a custom conversion code to make the TDR generated by SaveTDROffsetsToFile have the same XML structure compatible with DPE.