Um, parents can be protective of their children long after they have outgrown them. My parents are still quite concerned about my sister's dating life despite her being over 21. Some parents are like that, it doesn't need to be about them being autistic but them being their child, and we do see people being a bit more protective of Renarin, ex. Dalinar along with Shallan, Adolin, Navani, and even Jasnah. Being an adult means nothing to parents. Whether or not it's yucky is kinda besides the point, it's a common thing that people can and will relate to.