To say that grease is a feeble anti-sieze is not really correct. As we know, grease is essentially oil (mineral, synthetic or veg) thickened with soaping agents to increase viscosity and oils are of course excellent at preventing seizure. Yes, other agents can be added to grease to improve certain characteristics but any decent quality grease will do a very good job of slowing the onset of seizing, oxidation etc. In other words anything is better than nothing (obvious maybe!).
Yes there are greases specifically designed to prevent seizure even better than 'normal' greases (more relevent at extreme high temperature and/or pressure but still applies to simple applications like a bicycle assembly). Greases sold as "anti-seize" will contain a powdered additive which is usually a transition or post transition metal (periodic table) such as zinc, copper, nickel, aluminium, lead, or sometimes other substances such as lithium, molybdenum disulfide or graphite. Or combinations of the above. All of these are anti-seize and will do the job fine on a Ti seat post with alu frame. Anti-seize grease does not have to be with copper (as shown by the fork photo posted above).