That’s why I said false negative. The medical test is testing for the presence of a disease. So if they find the disease is considered a positive test (it found what it was looking for). For static analysis on code, its the opposite. Its testing if your code is free of issues that it can detect. If it finds no issues, then the test was positive. If does find issues, the test failed and each issue is a negative that contributed to the test failing.
By your logic it would be a positive for your code to have errors/warnings. And on the latter, that would appropriate if there was a test that determined if you are free from all known diseases (or at least those that it can detect).