Can you tell the difference between a human and a midi sequencer performing the same piece? Yes, of course you can. The difference is feeling.**
Allow me to elaborate. If you were to program the score into a midi sequencer, meticulously following all dynamic (via velocity), articulation (via duration and velocity), and tempo markings, you'd end up with a midi performance which does "what is on the page" by following these instructions. Despite following the same set of instructions, this midi performance can still be differentiated from a human performance because the human will be adding extra detailing and shaping to their performance, thereby imbuing it with an emotional quality which cannot be strictly notated, ie this elusive "feeling". There is an emotional meta-layer to the human's performance which the sequencer's performance lacks.
This "feeling" is achieved by varying the envelopes of the various parameters of sound, such as by adding vibrato, pushing or pulling the tempo, or by shaping each note dynamically. To a certain extend, a human will do this naturally without thinking, but a big part of your job as a performer is knowing when and how much. This is where interpretation comes in. You need to see through the limitations of notation and identify what the composer is trying to convey, and then fill in the gap. (As an aside, a skilled composer will make this easier for you.)
(Yes, this extra detail can be added to a midi performance, either by simply "recording" a human's performance or through meticulous editing, but that is not what I'm talking about.)
my only conclusion is that they didn't want me to play what was on the page
You are supposed to play what is on the score, but you're supposed to play more than what is on the scorethat. Musical notation has its limitations. Your job as a performer is to interpret the score and turn it into an emotionally compelling series of sounds. You will not fail your exam unless you grossly misinterpret the score and the composer's intent. This expectation of interpretation isn't obvious to english speakers because 'performer' and 'interpreter' generally mean different things. But in other languages (I'm thinking Romantic languages specifically) 'performer' and 'interpreter' are in fact one word.
Perhaps the problem is that you're too focused on the technical execution, which isn't leaving enough processing power for interpretation. You should know your material so well that you don't need to think about it at all.
An anecdote: When I studied classical guitar in university, I learned a piece which was call "tears", but in a language I didn't know so I didn't get the obvious suggestion from the title. Just like you, I played all the right notes in the right order at the notated tempos and durations, but my teacher kept telling me that the feeling was wrong. After spending most of an hour-long lesson playing the piece over and over, with seemingly no progress, I was visibly frustrated and demoralized. Finally, he sang the piece to me, using his voice to convey the feeling that my performance lacked. It seemed exaggerated to me at first, but suddenly I could hear how the music was heaving and sobbing, dripping with sadness. The feeling was visceral. Then I played it again, aping his expressiveness, and instantly it was better. He sang along with me and it got better still. I continued to practice it this way and soon I could perform with convincing feeling. You need to do this with each and every piece you learn. Get inside it, see what the composer is trying to convey, and then bring that out by exaggerating certain aspects of your performance. Tastefully.
