Now, you don't know that for sure. Did you see any remains of exhaust valve stem seals? Some engines did not even have them. They really aren't needed. Earlier engines never had them. If you can see no evidence whatsoever, it probably didn't come with them.
Glad you brought this up. I put a bunch of valve seals on engines while still in the car and I was taught by my mentor that you only need them on the intake valves. So this is the way I've done them for 48 years! Tho most people doubt me.