explain this combat mechanic?

So for the description of the summons "Familiar" in the bottom right are three spells. Why are those there? The familiar does not have immediate access to them as far as I know. As well, in this case, the familiar is unable to cast spells on the overland map.
Second, what is the point of giving summons the ability to cast spells from the sovereign's spell book if they essentially have no affect since they are based on intelligence? For example, a familiar cast "Haste" on someone gives it .1 extra action points during combat which does not even appear in the action points of the unit the spell is cast on. As well, as summons level up they do not seem to increase their intelligence so that's out too. So why do they have the ability to cast spell book spells? (Not in a mean/snippy tone. just curious)