There is no separate product - it is a feature of the main product. Please point out where documentation says it's for enforcement because that will need to be corrected. It can help teachers educate students about plagiarism but it's not meant for enforcement. It's a student tool.
Here is the text from the linked landing page describing the plagiarism checker feature (emphasis mine):
Our free plagiarism check will tell you whether or not your text contains duplicate content. Our Premium plagiarism check highlights passages that require citations and gives you the resources you need to properly credit your sources.
This makes it quite clear that is an authoring tool, not policing tool. Plagiarism masking is not addressed by design. It's a trivial thing to code if there was a need but the company made a decision to stay out of plagiarism enforcement (at least for now).
Here is the text from the linked landing page describing the plagiarism checker feature (emphasis mine):
Our free plagiarism check will tell you whether or not your text contains duplicate content. Our Premium plagiarism check highlights passages that require citations and gives you the resources you need to properly credit your sources.
This makes it quite clear that is an authoring tool, not policing tool. Plagiarism masking is not addressed by design. It's a trivial thing to code if there was a need but the company made a decision to stay out of plagiarism enforcement (at least for now).