The issue with winter weather is not just the cold temperature. It is also affected by moisture condensation, moisture penetration into the crevices and then freezing.
Reading the many user issues of frunk and door handle problems in this forum, I think the pertinent question to ask is whether Lucid's "cold testing" is just cold-dry temperature or does it include moisture penetration.
A simple cold temperature test might confirm the car functionality when the temperature is low (e.g., below freezing). In reality, weather factors such as freezing rain, moisture ingress into the crevices and rubber seals (gaskets) from multiple freeze/un-freeze cycles can easily explain the type of problems (e.g., frunk frozen shut) owners are experiencing. These moisture-ingress/freezing-shut issues affect other cars, EVs or ICE cars, as well. The pertinent question is whether Lucid did this type of testing in their internal certification.