in order to summon 2 piglets you'd have to have piglet in the pool twice, Similarly if Ramos wanted to summon 3 spiders he'd need 3 spiders in his pool.
Basically it does give summoner over 20ss to play with [for example dreamer being a summoner means you've spent a max of 35ss on models from your pool, as his upgrade isn't declared in the pool which means he actually can get 25ss more than his crews starting size]. Once a model dies, it can be re-summoned, however if you wanted to summon multiples of the same model, then you would need multiples in the pool to start with.
The aim of this is to give new players a taste of playing with a pool of figures, that they can mix between in different matches, whilst not having such a large pool that it is intimidating for a new player.
I know a number of experienced players are planning to attend and all seem to be keeping with the "use a new crew" mentality, from those I've spoken with