I think it’s cultural and they do autonomously during in Windenburg. I saw first time when premade young adult sims kissing but they aren’t lover. Then I saw my sim do this with other sims even no romantic relationship.
You might be able to see this greet when you stay on community lots or event and wait to see sims do it. I don’t know the criteria, it’s not 100% happen, maybe a random chance or need to be friend. I will recheck later when I found again.
If I remember right, Selvadorada has unique “friendly kissing” greeting like this too. Might be European culture reference.