>that doesn’t mean that editing or inserting values to dnsmasq as an unprivileged user doesn’t exist as functionality in another application or system.

The developer typically defines its threat model. My threat model would not include another application inserting garbage values into my application's config, which is expected to be configured by a root (trusted) user.

The Windows threat model does not include malicious hardware with DMA tampering with kernel memory _except_ maybe under very specific configurations.