> "Email open" tracking just got a lot more reliable for all mass email & marketing automation vendors.

No, it didn't. If you had chosen the option to ask before displaying external content -- which existed and applied to non-image content and, without which selection, email-open tracking by external non-image content was already reliable -- then the new setting to ask before displaying external images is selected for you by default.

If you hadn't selected that option before, you weren't protected from "email open" tracking.