This exactly what has boggled my mind. Using the unseen tactics and the fact that if PCs are rolling initiative then they really already assume an encounter is imminent. I have been playing D&D for 23 years and Ive played Pathfinder 1sr edition since it has been out. What is going on with surprise rounds? Can I at the least get one action off? These rules are not very clear cut and I understand that it is a playtest but why is it that the only thing in the book in the index references the Rogues Surprise attack. I can understand if only players who are aware get one action but the fact that surprise rounds are based solely off of being seen, unseen, makes no sense.
For example you come around the corner with a torch where several goblins are mining and two are on watch. Seeing the light shining from a nearby corridor the goblins; use their action to alert the other goblins who are working, prepare to use their action to shoot arrows once the PCs round the corner, or some other action. The PCs would have a chance to hear the nearby noise of clanging pickaxes.
Now some might add well you could always allow them to ready an action. But it would be nice for some clear cut rules. I apologize for the rant but it just upsets me that there isnt a clear cut way or an example in the playtest rules. If I have overlooked something please point me in the right direction.