Response headers update with declarativeNetRequest update rules not visible in Chrome's DevTools

Question

In my chrome extension V3 I use chrome.declarativeNetRequest.updateSessionRules to modify response headers:

chrome.declarativeNetRequest.updateSessionRules({
    addRules: [
    {
      id: 999,
      priority: 1,
      condition: {
        initiatorDomains: ['localhost'],
        resourceTypes: ['main_frame']
      },
      action: {
         type: 'modifyHeaders',
         responseHeaders: [
            { header: 'Content-Security-Policy', operation: 'remove' },
            { header: "bar-foo-baz", operation: "set", value: "true" },
        ],
     } 
   }]
});

The test I do is pretty simple. I violate the Content-Security-Policy rule so I get an error in the console. But when I apply the remove operation all works fine and the error is gone.

But the weird thing is if I look in the DevTools Network tab, I still see the Content-Security-Policy header and I don't see bar-foo-baz.

Does someone know why this is happening?