@dominiks best practice would suggest not to use undocumented APIs, these might be left over from an older version in new versions to allow customer time to refactor code/apps. Using undocumented APIs is time-consuming for everyone, and much more error-prone than working with a well-documented API. The end-result could be that your company uses/provides an API that is no fully tested, with functionality and security flaws etc.. I would open a TAC case or ask your AM for this to requested that engineering team comment on use of these.
Hope this helps.
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