Was your ECU cleared by the service technician at the dealership/garage when you brought it into them or did this happen before you brought it to them to service?
Reason I asks is I accept that my ECU may have been cleared when the battery last died a few months ago, but I'd estimate I've done 2-3k KM since then so if I understand the issue correctly, this mileage should be enough to be able to perform the hybrid check.
Also, the dealer mentioned low voltage was the reason they couldn't do the hybrid check, didn't mention anything about ECU being cleared