You as a learner copypasting code isn't itself the problem. The problem is that this is a published, copyrighted work that has been included into another publis

You as a learner copypasting code isn't itself the problem. The problem is that this is a published, copyrighted work that has been included into another published, copyrighted work without adherence to license terms. If I had copied Culture4Life's code and used it in my own project, they would be suing for tens of thousands of dollars in damages; and the law would agree that I should have to pay tens of thousands of dollars in damages for that infringement. Asking for attribution and a proper license declaration is the polite way to handle a license violation.