I have a question here: does that means the crews will / should follow the spirit but not the letter of the SOP?
No I don't think so. I think that in 99% of cases SOP's should be followed to the letter. If they can't be then they should be re-written.
Many pilots don't understand how SOP's work. Sop's provide a 'framework'. If they are followed then both crew members know where abouts they are within that framework. If pilots start changing the order, omitting steps or even changing words it reduces the effectiveness of the Sop's and reduces their effectiveness. If an abnormal situation is developing and the flight is progressing within the Sops it is quickly apparent that something is not right. If the flight was operating outside of the Sops or only losely following them then it is difficult to tell if the abnormal is a result of the current way of operating or is an abnormal.
Even very simple things can cause extra unneccesarry workload, eg the standard call for raising the gear is normally "Gear Up". If you are flying with someone you don't know and English is their second language and you call "positive rate" and they say " ahhh yeah we take the gears up" you have to think to yourself "
that wasn't what I was expecting...what did he say?? everything seems normal....ahh yes I know what he said..." and then you take the gear up. That may only take one sixteenth of a second for your brain o do that but it is the process you go through ad after a few days of it you will start just doing what you expect he/she wants without listening too hard. The other day I expected a Flap 30 call and selected flap 30....what he had actually said was something like " ahhh please I would like flap 25"
So following SOP's even down to exact standard calls is important in my view.