pacino and de niro didn’t rehearse the diner scene! 
indeed, i believe they may have been aiming to capture a kind of verite, each approaching the scene as strangers, reflecting their characters approaching each other as unknowns. a simulation of reality, yet “somehow more real than reality” itself. thus:
The postmodern semiotic concept of “hyperreality” was contentiously coined by French sociologist Jean Baudrillard in Simulacra and Simulation. Baudrillard defined “hyperreality” as “the generation by models of a real without origin or reality”; hyperreality is a representation, a sign, without an original referent.
