is there life beyond cloud cookoo? part 1, page-13

That's pretty much right

A PFS is an indication.

A BFS is more of a detailed budget.

A BFS costs a lot of money to prepare, and take time which is also precious - SO before you go and blow all that dough, and time, you want a "preliminary" indication of whether it will all be worthwhile

A PFS may give you the costs associated with several mining and shipping processes, call them A, B and C..
And then once you've picked one, say A, the BFS will work out to the dollar what it will cost (plant, equipment, production costs based on values at the time etc)

We're talking about studies which normally take between 2-3 years to prepare in total and cost a lot money -

MOST OF THIS WORK HAS ALREADY BEEN COMPLETED SAVING US 2-3 YEARS AND OVER $20M!!!

Hence, the current exercise is more of a "confirmatory" study than a PF of BF study!