Thank you for the feedback -- I agree more context and explanation is needed for each of these tests.

In the Blob case: the test code is storing a unique string in a Blob URL under one website (first party), and then attempting to read back that string under a second, different website. (See "result, different first party".) If the string is accessible under a different first party, then it is possible to use a Blob URL to track a user between two different websites.