In his book A Pianist's A-Z A. Brendel writes:
[This is my clumsy translation from a non-English edition. If you have a proper English quote, please replace this with it.]
"Syncopated notes should not sound like regular notes. When they enter the next rhythmic unit, their ponderousness must be distinctly heard. Each syncopated note carries its accent, one that must be stronger than other accented notes of the same length. Rendition of such notes requires a specific movement that gently pushes the wrist in the direction of the piano's lid1."
1 It's not clear if here he means the lid or the fallboard.
What kind of movement has he in mind?