Some URL scanner detects a given URL but its corresponding antivirus solution does not detect the downloaded file, or vice-versa

Very often URL scanners and antivirus engines are independent solutions even though they may belong to the same company, hence, detecting a given URL as malicious does not necessarily mean that the file located at such URL will also be detected, and vice-versa.

Moreover, sometimes the URL might be malicious (e.g. phishing site) but the downloaded file (HTML of the phishing site) may not necessarily be a threat for your computer. Other times, the downloaded file might indeed be flagged by the antivirus signatures but the corresponding URL scanner might still have no knowledge that a given URL is distributing such file.