"How can we ever truly know if we are hearing exactly what is on the recording?"
Perhaps unintentionally, I actually think this opening question on this thread is fiendishly complicated. (Or perhaps it simply asks the wrong question.)
It's complicated because it implicitly embodies the question of what is one's objective of high-end audio.
A group here developed in 2016 four alternative, but not mutually exclusive, objectives of high-end audio:
1) recreate the sound of an original musical event,
2) reproduce exactly what is on the tape, vinyl or digital source being played,
3) create a sound subjectively pleasing to the audiophile, and
4) create a sound that seems live.
So, in the opening question, is the "recording" being referred to whatever sound is coming out of the grooves of the record as you spin the vinyl, or is the "recording" the sound of the performance which the recording engineer attempted to capture? Before one may even begin to address the question, one must understand exactly what is the question.
If the former, one is focusing on Objective 2); if the latter, one is focusing on Objective 1).