This is indeed broken, and it is strange there is no 'fix' or if they have acknowledged that there is a real problem with this. I started a new save to test (this is post update) in normal mode, and I created a standard YA sim and moved her into a regular home, she had already lost 3 days in her lifespan on the first day of creation. I wanted to see how the other sims were age-wise, so I went around playing different households and every YA sim had the exact amount of days being 24 days (no less or more). My sim had 21 days left and she was freshly created. I also tested the short and long and every single one still had 24 days the numbers didn't go up or down and remained the same.
I did of course test out children, teens, adults, and elder sims to see where their numbers were. Children and teens have exactly 13 days and adults have 24 and elders have 60 days, and this is all on normal mode. Again, changing the length does nothing to these numbers and they remain the same regardless. I also checked saves I have since may (glad I kept some old ones) and those are also affected by this glitch, I did also back up saves before the patch and put those in and they are all affected as well.