Comment by nh2
I quoted the documentation that claims _something_ is pipelined.
That is extremely vague on what that is and I also didn't check that it's true.
Both the original claim "the issue is the serialization of operations" and the counter-claim all sound like extreme guesswork or me. If you know for certain, please link the relevant code.
Otherwise somebody needs to go check what it actually does; everything else is just speculating "oh surely it's the files" and then people remember stuff that might just be plain wrong.
Speculation isn't the most useful thing, but saying "that is not the question" to valid speculation is even less useful.