Stackoverflow should do a proper cleanup on questions before migrate to PSE. See this example: Getting started with open source. It has multiple duplicates including this migrated question: So I want to get into open-source programming
Stackoverflow mods/community will throw question as they want and PSE mods/community should give the proper handling for SO's messy?
SO people should managing the topic properly and when it get organized then it can be migrated to PSE. Sweep the trash to neighbor is not the solution. Otherwise or SO never get organized or SO will just push the problem for another site.
We PSE people will merge our questions with SO questions properly migrated but we don't do the SO's job merging their duplicated questions.
It's just a example of the upcoming problem. These specific questions has another problem, see: Migration questions from SO to PSE just to stay temporarily