CodeIgniter 4 base_url() bug

1. base_url() . 'favicon.ico' . '?' . 'v101';
2. do not use base_url()
3. base_url('favicon.ico' . '?' . 'v=101')
4. configure caching on the server.

1. I know, but this is not fixing a bug in the framework. My thread is not call for a help, but a bug report. There is no problem in CodeIgniter 3.
   
2. Why not to use base_url()? It should be used for files instead of site_url(), like it is in the documentation.
   
3. I did not get the point. This is exactly what I wrote what is causing the problem.
   
4. No, it is a good practice to do it the way I am doing it to get an immediate effect. But maybe I am doing it wrong (tell me why).
   

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3. base_url('favicon.ico' . '?' . 'v=101')

Oh, I get it. My mistake. I understand why it is adding an equal sign at the end now. In my case it is considered as the parameter name and expecting a value.