I very much would not use the OBD port or any other permanently powered 12V, regardless of what the manufacturer of the plug claims. All it takes is a faulty plug, and your car is out of commission for potentially weeks.
Hyundai EVs did/do have an ongoing issue with ICCU/12V failures, leaving cars stranded/bricked. I would not use the 12V supply while the car is off, period.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.