I can’t imagine that it will be any more or any less secure than other vehicles. One thing that deters break-ins is full internal visibility: If a miscreant can see there’s nothing inside to remove they’ll move on as it’s not worth the effort. The lack of door handles and the small openable door windows might serve a similar purpose as most automotive break-ins rely upon speed and ease.
Given the recent trend of casually keying of tesla cars I think a related question would be if external cameras can record in a sentry mode. We have external cameras for mirrors, likely something in front for FSD and rearview.
I am also curious how scratch able the unpainted polycaronate will be. If its anything like a motorcycle helmet it might be nearly impossible to key an Aptera.