I do not think the processor was designed to improperly unwind from speculative execution, such that the state after failed speculation is not identical to the state prior to speculation.
But yeah, this an old discussion, and a deep rabbit hole. There's many layers to consider bugs at. Implementation can differ from developer intention, developer intention can differ from group agreement, group agreement can differ from design document, design document can differ from product development intention, and product development intention can differ from communicated functionality.
I'm betting this would be implementation differing from developer intention, although I would consider (almost) all of the above to be bugs.
But yeah, this an old discussion, and a deep rabbit hole. There's many layers to consider bugs at. Implementation can differ from developer intention, developer intention can differ from group agreement, group agreement can differ from design document, design document can differ from product development intention, and product development intention can differ from communicated functionality.
I'm betting this would be implementation differing from developer intention, although I would consider (almost) all of the above to be bugs.