Seems everybody has a different definition about canary tests. My view of a canary test is something that periodically checks/tests something. For example, recently cloudwatch(aws) released canary-checks and it allows you to call endpoints or aws services to perform healthchecks. There is also checkly(api specific) or datadog(generic purpose monitoring).
Ive used checkly in my personal projects and cloudwatch at work to monitor healthcheck endpoints.

The scenario you mention sounds close to feature-toggling making certain features available to certain users/clients. Is that the case? I have no experience doing that.