Lactate's available in the internal engineering data of these sensors, just not something that anyone has wanted to spend the time or money to qualify with the FDA. It essentially comes "for free" due to the chemical reaction the sensor uses.

I think you are misinformed: the electrochemical reaction used by continuous glucose sensors relies on a glucose-specific enzyme and it doesn't have anything to do with lactate. Lactic acid strips use a completely separate enzyme/reaction.

Hat tip to you and sibling comment about continouous lactate sensors (seem like they are microneedle/patch based?). Quick review shows minimal clinical evidence, but maybe that's sufficient for the consumer wearable market.