Honestly the worst thing about it is that you have to manually check to see if your battery is affected. A proactive email might be better than telling people to enter their serial on a site to check.
I can’t imagine Apple, a champion of privacy, wants to keep a mapping of serial number to user emails. Even if harmless or if it already exists, it might taint Apple with a creepy vibe.
I had to check myself, and there are serial/IMEI numbers there, at least the last-five version of each... maybe they store partial hashes instead of the full numbers (hopefully, but I'm a pessimist)
Apple's has shown on multiple occasions that it's more than happy to have rules for third parties and the ecosystem that are different from the rules it has for itself.
You can't use iMessage without a valid Mac SN, for example.
We already get alerts for "your battery needs service" or "your operating system has an update available". I don't see "your device has been recalled" as being outrageous.
Or just some sort of OS X notification/pop-up. Since they don't notify the customers, even though they have the means, it looks like they're doing the recall for liability reasons only and want to actually replace as few batteries as possible to limit the costs.