Hi,
as of now you guys are correct - and there is no graceful solution.
The problem is that the browser hosting the login has no cancel option as of today - so TMM has certain ways to customize the login view (like background color and other elements); but a Cancellation token is not part of this config.
Otherwise we have no control over this.
I'll make a feature request to see what we can do here. This is nothing short-term - but we'll look into this and make the corresponding feature requests ourselves if needed (my guess).
Regards
Nico