I got confused too at first but after Hoyeong (The current Oracle) got stab by Woo (who become the vessel of Imugi) the Bead got out of Hoyeong Stomach. We see that it shift to the Past where the curse all started. So all the descendants of 4 family is present there. It's not a time skip but a revelation how the curse started and fall to the 4 Family. Thats why all the characters from the past looks like the previous/current characters from the main Story.
I got confused too at first but after Hoyeong (The current Oracle) got stab by Woo (who become the vessel of Imugi) the Bead got out of Hoyeong Stomach. We see that it shift to the Past where the curse all started. So all the descendants of 4 family is present there. It's not a time skip but a revelation how the curse started and fall to the 4 Family. Thats why all the characters from the past looks like the previous/current characters from the main Story.
Hope this will help.