Thank you for reporting a bug to Unity.
We have reviewed the issue carefully, and in this case, the team is unable to prioritize fixing this bug. There are a number of reasons we make this decision, including the impact and severity of the issue across our user and customer base, and the possibility that future plans may solve the problem in a different way, or that a workaround for the bug may be available.
Today we will be closing this case. Thank you again for taking the time to report this issue, and please let us know if there is anything else that changes the impact or severity of this issue.
WORKAROUND NOTE: The bug appears to be exclusive to the old Input Manager and not present in the new Input System, you can use Input System's Mouse.current callback to workaround this issue (https://docs.unity3d.com/Packages/com.unity.inputsystem@1.8/manual/Mouse.html)