Page CSP breaks Element Picker

Description

Several different CSP directives can cause different kinds of breakages in the Brave adblocker's element picker UI.

Blocking scripts via an explicit or implicit script-src: 'none' directive causes the page to turn blank during element-picking. In most cases, the element-picker still works; users just need to remember where the desired element is located and click that area, blind. In at least one case, the rules-box failed to render altogether.
A sandbox directive that lacks allow-same-origin and/or allow-scripts will allow the element-picker to show, but render it non-interactive.

Visit https://seirdy.one/meta/csp-bug-reproduction/
Follow the steps on the page to re-produce the issue with four different Content-Security-Policy headers. Observe that the fetch directives on seirdy.one alone are enough to hide the rules box and turn the page blank. The sandbox directive without allow-scripts allow-same-origin renders the element-picker completely non-interactive.
For comparison, test on https://grapheneos.org which allows scripts from self.

Consistently reproduced.

1.47.55 Chromium: 107.0.5304.91 (Official Build) nightly (64-bit)

I've been encountering this issue for months, so it should be visible in the stable and beta channels too.

For comparison:

uBlock Origin for Firefox only breaks upon encountering a sandbox directive without allow-scripts allow-same-origin; fetch directives do not break it.
Adguard's experimental Manifest v3 version works perfectly well in Chromium on CSPs with sandbox allow-same-origin. Its element picker fails to load JavaScript if allow-same-origin is not present.