Although I won't use Smart Summon for moving the car in/out of the garage, my impression is that regular summon is safe. My understanding is that regular summon only moves the car straight forward or straight back. I tested by turning the wheels to their limit, and indeed, the car straightened them out before moving. However, I did notice a slight turning of the wheels as it got into the garage. That is, I expected them to stay exactly straight, but they turned by a very small amount. What's up with that? Is it making a midcourse correction to keep it going straight? If so, is it acting on GPS data or what? Also, do you agree that using regular summon and watching the clearances is safe? Finally, I wonder if there's a way to make the garage door side jamb more noticeable to the car (white tape?).
Regular summon uses the ultrasonic sensors for obstacle avoidance. I line my car up perfectly to pull into the garage, and while I don't think I have an especially tight clearance, the first thing my car does upon regular summon is turn the wheels pretty sharply to the left, presumably to avoid the garage door jamb on the right. Unfortunately this is right towards my wife's car, which the Tesla sees a moment later and then decides it can't make it. So no, your assumption that a summoned car will go perfectly straight is incorrect. It will use its sensors to avoid obstacles, and thus I would say that I do agree that using regular summon is usually safe, even without you having to specifically watch it (although I would always recommend you do keep your eye on it). In my case it's apparently "too safe" and refuses to pull into my garage most of the time (and yes, I do have my summon settings on "tight").