Absolutely. For debugging purposes, browsers should have a mechanism where you can purposefully use your own local certificate, with a big unremovable warning at the top telling you that. It should not, on the other hand, ever look like a valid secure site.
No legitimate reason exists for a browser to silently show a site as secure that uses certificate pinning and doesn't serve the pinned certificate. Ever. For debugging purposes, you don't need it to work silently.
And if someone started intentionally compromising browsers to make such warnings go away, we'd have a clearer indication that they'd progressed past ignorance into malice.