I also just had a teen grow into a YA using a Celebration stuff Birthday cake. I do indeed have the YA cake but that was not the one I was using.
So does this mod change it to where the default is that teens grow into YAs, and the YA Cake keeps them from doing this? I read it the other way around, then.
I then used Simlogical's Cake and the sims aged into a just about-to-die elder! I paused and aged her down into an adult, and then pondered what the ramifications of that might be, and then quit without saving.'
I only had a handful of sims that geographically live very near to a college so I thought it would be nice if they could live with their parents and commute to school. I'm hoping I can figure out proper use of this hack.