pikachu, I believe you have a very long five months in front of you, LOL.
Does it appear he's having difficulty getting in the car, because that might give you an opening to ask him if he's having difficulty. Possibly he'll say something that will make his backside more acceptable to you.
When you said he can't drive due to health problems, my first thought was that maybe those problems cause him to get in this way? In addition to balance, there can be some twisting involved getting in sideways. Maybe that is an uncomfortable motion for him?
My mother had knee surgery and this is how she got in a car. She was able to pull her legs around because they didn't bend good. This is how she was taught to get in the car after surgery.
You don't have to attend every argument you are invited to.
When I'm having knee issues (as happens periodically), I tend to get in this way. Then if anything "gives out," I'm less likely to fall, since most of my weight is already safely plopped into the seat of the car.
Pikachu, I love you to death, but I think this is just a personal issue that you're letting get to you. Are there other things about this guy that bug you, and you're just using this as a handy specific point to be irritated about?
My hubby does the exact opposite. When he goes to get out, he often has no feeling in his right foot so he has to turn back to his seat, put his hands down in the base of it, and wait for enough feeling to balance himself. Luckily for the public, he has a very fine derrière.
I've known people with health problems get into cars all different ways. My cousin used to have a terrible time, especially in my former sports car. It was low down and small and she really stuggled. I had to help her a lot. She has knee and back conditions. And when I had two frozen shoulders...........OMG. Doing anything was a struggle. I had to ask for help with my grociers.
Please know that IMO, having mobility issues is very embarrassing and the person would give anything to not be awkward or call attention to themselves. It just can't be avoided.
Perhaps the guy will improve with his mobility as his medical condition improves.
Look away. I'm sure he doesn't want you staring at his butt. Once he's swinging his legs in, securely in the car, you can acknowledge him.
Count your blessings!
I realized yesterday that some might miss-see my avatar as a reference to my American public "sheep" comments. Which it isn't.
It's llamacorn. A llama with a unicorn horn. It was on one of those ads that play on a Youtube video before the video itself.