Difference between current sense amplifier filter configuration
Does it change something by connecting C3 to GND of 1.65V ? Is it
  correct to say that in AC 1.65 and GND are connected together so C3
  connection doesn't care?


That is correct. As far as AC is concerned, a DC voltage source is the same as ground so, providing your mid-rail generator (1.65 volts) is bolstered up with bulk capacitance (if needed), it should behave the same.