Not necessarily.
You can summarise while you redistribute, OSPF being a good example, but summarisation is not just to do with redistribution.
It is actually a very important part of network design because it can keep routing tables manageable, it can limit routing queries and updates and it can also be used to influence traffic paths.
Whenever you have multiple sites connecting to a WAN for example it is usually always a good idea to design your IP addressing so you can summarise the whole range in use at a site to the WAN.
There are occasions where it can lead to suboptimal routing because when you summarise you don't always have the best information but as a rule it is still a very useful thing to be able to do.
Jon
