In my view, there are two types of table variation, positive variation, and negative variation.
Positive variation is a recognition that every table is different and every situation is different, and a lot of role play comes down to judging attitudes and intents and making the best call for the game. None of us want PFS to turn into a computer RPG with fixed scripts, limited choices, and fixed outcomes. (I hope)
Negative variation is the reasonable (I think) desire that players be able to predict the possible and likely outcomes of their actions with some degree of success. That is not to say there shouldn't be surprises, but, for example, if I have a jump skill of +5, and I have a running start toward a 5 foot gap, I should not find out half way across that the GM is using a rules interpretation where I have a 20% chance of falling. Likewise, the same behavior in similar circumstances with similar outcomes should not result in radically different rulings.
I want to maximize the positive variation, and minimize the negative.
Run as Written vs Rules as Written:
I feel obligated to point out that PFS does not have a Rules-as-written rule anywhere in it. It *does* have a Run-as-written rule. Which is defined in the guide as "you may not alter any number specified in an encounter, or contradict a published rule or a leadership forum post. But you are required to use your judgement to add circumstantial bonuses or penalties, to add environmental hazards (if the environment is described but not statted), and to decide areas where the rules are unclear or conflict.