That's when I realized it too. Told my wife they fukking with the timeline when I saw the young version of him and his sister. Then Yen talking bout how she been a mage to royalty for 30 years and shyt. I'm not sure if they were purposely trying to fool people with the 3 different timelines or if they just kinda fukked up in the presentation, cause other than Foltest nobody showed any signs of aging in the different timelines. Dialogue was the only reveal and if you not paying attention it's easy to miss.
Witchers age very slowly and Mages can stretch their lifespans for centuries.