I've regularly found that military city states give you outdated units. Over about 50 turns the city state can give you an anti-tank gun, then a longswordman, then an infantry. I've been given scouts in the 1400s. I've no idea at all why this should be happening but it doesn't feel like a feature. How bad do the units have to be for it to be a bug? In the attachment the city state has given me a longswordman in 1940 when I'm building the spaceship. The previous unit it gave me was an anti-tank gun which seems much more reasonable! Both city state and myself have mechanized infantry on this screenshot, the mech being the top level upgrade for a longswordman.