Know fights does not necessary mean completed fights.
Are you joining a pug for the first 4 bosses of ICC? Tab out and spend 15 mins on youtube watching a few video's.
Make sure you use DBM or a similar addon as well as debuff timers.
Basically anything that will help you react quickly to things that you know will happen from a reading up on the fight standpoint but have never personally experienced.

The reason people want experienced people in their pugs is that as a RL in a pug you have to deal with not knowing everyone, half the dps is wispering you that they want to roll tank or heals for main spec. Their bff or bf or sister's dog needs into the raid, they need to go afk for this or that reason. Explaining the fights in depth becomes an extra hassle that you can easily get rid of. Regardless of how many people have done the fight I do a quick overview of how WE are going to do it so if you've watched a video and you listen there you should be fine.

TL:DR Take responsibility for your own raid knowledge even if you havn't experienced it before.