I would add that I have had my fair share of industry scale problems where labeled data is not drawn from the same distribution as where the system will be depl

I would add that I have had my fair share of industry scale problems where labeled data is not drawn from the same distribution as where the system will be deployed. But as you pointed out earlier, there are theoretical and practical methods to deal with this. For someone who wants to get familiar with this territory, domain adaptation, transfer learning, transductive learning, semi-supervised learning, etc would be some of the keywords to seed an initial literature search with.