The Bolt technician at our local dealer has agreed to put my car on his OBD reader, which is amazing given the pressure on him to swap batteries. I'll ask him to check Ah capacity. It's possible my EngineLink measure isn't accurate for some reason, or maybe he has a different way to measure capacity that I'm not seeing in Sean Graham's spreadsheet of OBDs.
Thanks Voltar, Gjetson, and Toyotiac for your help! If you think of anything else, please let me know. This concern about capacity, unfortunately, takes a bit of the shine off having a new battery. After getting on official record of the capacity from the dealer, I'll just live with the battery and see how it behaves instead of fussing over it.