There was very interesting post:

Certification covers 5 languages and several different levels in each. No-one has got complete certification. In many cases the test specifications have not even been written yet...
..When the standard originally emerged many years ago, manufacturers had to decide whether to throw out everything they had done up to that point and start again, or stick with what they had and adapt it. For some languages like Structured Text there wasn't a high level of previous use so generating a new editor to comply with the standard didn't upset manufacturers or their existing customers too much. However for Ladder or Instruction List, everyone already had their own dialect and the larger an installed base a manufacturer had the more reluctant you can understand them being about changing.

However, post is absolete (2005) and afterwards Codesys got complete IEC61131-3 certification.

As for Siemens, the only thing we have at the moment is a table on PLCOpen with 2 compliant languages from Siemens from 1998 and 2005.

Last thing I can suggest is to write official letters to Siemens and PLCOpen for further assistance and conformity confirmation.

Have a good day!