Apex Test Failure due to 'Connection Canceled' seen in UI but not in Deployment

During deployments, we do not do fixed test run time limit checks, whereas via the UI we do (either 'Run All Tests' or running a test for an individual class). In the deployment context, this limit is a bit relaxed. If the differences between the test failures seen in the UI compared to the deployment are solely down to 'Connection Canceled' errors, then this can be deemed expected behavior as we intentionally do not do this hard check in a deployment.

NOTE: Same behavior can also be observed when simply running tests outside of a deployment/validation scenario via the Metadata API, again this is expected behavior