I don't have any concerns about allowing questions about recorder.google.com if they are a good fit for the site.
Given the limited functionality and purpose of the web app, I'm not sure what a good question would even look like but I'm open to the possibility.
As noted in the question, recorder.google.com is an extremely limited web app that provides access to recordings backed up in a Google account from the Recorder Android app on a Pixel phone (see "Recorder settings > Back up & sync" in the Recorder app).
The Recorder app is a competitive differentiator for Google Pixel phones and is unavailable on other Android phones.
While the web app provides some limited tools for recordings backed-up from the Recorder app, it provides nothing if you don't have a Pixel, or have a Pixel but have no backed-up recordings.
The Recorder app support documentation never refers to the web app as an app or as Recorder Web but always as recorder.google.com
Back up and sync automatically saves your recordings to your Google Account at recorder.google.com
To find and manage your recordings in a web browser, go to recorder.google.com
I appreciate that by its nature recorder.google.com is a web app however questions need to be practical and shouldn't be like the following:
I use a web app that is intended solely to access the recordings backed up from a Pixel-only Android app to my Google account. It has some very useful features for those backed-up recordings.
It would be great if I could use the web app to upload recordings from other places instead of simply using it as a tool to access the backed-up recordings from the Recorder Pixel-only Android app.
I'm also curious for your example question, would you close it as "lacking details or clarity"? If so, why? In my opinion, that leads to a lot of time wasting as the question asker then tries to add details, only to have the question remain closed.
No. I would not. My example is sufficiently detailed and clear. It is not my intention to waste users' time. This applies to the ones who might try to answer insufficiently detailed questions, and also, to your point, it applies to users with clear questions that are not a good fit.
I would be likely to use a custom close reason similar to:
I am voting to close this question because it is at odds with the app's sole purpose which is to provide access to files backed up from the Android Recorder app to your Google account.