Thank you, JZ for your report — and Night Spring for his cautionary note.
Definitely endorse the idea of recording or taking screenshots of Apple Support's judgment of this and saving them as evidence. And, somehow, putting them on notice one's expectation is for the oxygen sensor to be enabled on the replacement Watch.
Wonder what recourse we'd have, though, if they promise it in a chat or phone call, and then the replacement doesn't have it. At a minimum, they should refund any AC+ renewal fees.
In one thread (on Reddit, perhaps), several users brought up the fine print in Apple's licenses that permits removal of features at their discretion. That’s chilling, dismaying, or boilerplate, but could give them a defense or justification for disable the oxygen feature.
Given that Apple is probably *importing* the replacements for coverage under AC+, the court-ordered import ban would apply and likely mean that the oxygen sensors on those would have to be turned off.
Given the uncertainty around all this, I'm leaning to not renewing AC+ unless I see an official Apple declaration that replacements under AC+ will have the oxygen sensor enabled or I come across a bunch of reports of Watch replacements that have it enabled!