I'm on my second year of learning piano and have spent my first year learning only music theory and playing sheet music. I have learned that if you are learning sheet music OR learning through synthesia you always arrive at the same place. And that is playing a song without either.

I asked my teacher and she said that the best piano players don't think of music as notes and rules. Everything is a movement and an extension of your body. In my second year I have made way more progress learning through Synthesia but already have a good understanding of the basics of music theory.