Is this a postulate? I get the expansion of the universe, the addition of discrete bits of space time between me and a distant galaxy, until very distant parts of the universe are moving relative to me, faster than the speed of light. But the other sure seems like (giant steaming load of convenience) I think I get reasons why, because they don't have any other way to explain the size of the universe and so on. Just seems it would be much easier to say the universe is eternal and cyclical in nature, and call it a day!
There are rules about things moving through space faster than light - there is no rule about space expanding faster than light.
As long as it can't be used to transfer information then there is no problem with relativity.