It looks like this functionality has been bugged since its release in v8.3.0.

Based on the following, it's possible that a regression occurred during a refactoring that was done concurrently with the feature addition:

• https://github.com/google/zx/pull/1001/files#diff-033ecd338eec0994fe53c0896219baee901e20068b8fbe6259a23d5759584b06L333-R340
• https://github.com/google/zx/blob/8.3.0/src/core.ts#L203C6-L208