That doesn’t sound convincing to me. The broadcaster should be able to know which mod is responsible, because the tool would perform actions on the mod’s behalf (with the mod’s token), so it should be possible on Twitch’s side to both log which mod performs an action and even how they perform it (which client id the token is from), so they could immediately be unmodded. If mods regularly choose malicious or unreliable tools causing havoc (and in the case of IRC-based tools for modding that could have happend already) or the mods themselves have gone rogue, then obviously they need to be unmodded because they can’t be trusted anyway. And these logs on Twitch’s side need to exist anyway, because even a mod using the official website could go rogue and cause major issues.
It might be possible for a clientside moderation tool to build a web app that allows a broadcaster to grant access, then allow mods using the third-party client to use that web app’s API. Building a web app makes sense when you’re already building tools for the web, like a dashboard for a chatbot or donation system, because you need to maintain that infrastructure and handle sensitive data anyway, but for an otherwise clientside application that doesn’t require this except to work around the Twitch API’s intentional limitation, it just adds unnecessary risks (because as we see time and time again, mistakes happen, security issues happen). I’d rather not add more complexity and more possible points of failure than necessary, but instead put time into improving the experience for my (and thus Twitch’s) users.
And if we go that route of building an intermediary API that forwards API requests from mods on the broadcaster’s behalf, then all those actions would appear to be performed on the broadcaster’s behalf. So even if it shows who performs an action on Twitch directly, it wouldn’t show the mod’s name. The broadcaster would have to look up who performed the action on the dashboard of the third-party tool (assuming logs like that exists there).
To me it makes a lot more sense from a security and usability standpoint to not add more complexity to a system, as well as for the mod that actually uses the tool to appear to the Twitch API as the one responsible for an action. Allowing only certain users access to those API endpoints (like editors) and logging mod actions (part of which already exists) seems like basic and important functionality that makes more sense for Twitch to offer themselves in a consistent interface, rather than having to go through multiple different third-party dashboards for each tool a mod prefers to use.