In Docs DXA / Public Content API, topics are given different IDs depending on the language selected (/api/<pub-id>/<topic-id>). For instances, the same topic might appear as:
EN: /api/123/456
NL: /api/789/012
It would be easier in some scenarios to switch between languages if only the publication ID changes but the topic ID remains the same. For instance:
EN: /api/123/456
NL: /api/789/456
In Tridion Sites, this works as expected for publications and pages.