Connecting a turntable fitted with 2x RCA sockets + ground post to the balanced XLR inputs of a suitable phono preamp will result to a balanced mode (just like if you were connecting a tonearm with a 5pin DIN socket). Of course, by design, the geometry of the RCA socket is not ideal for a balanced connection (nor the connection of any symmetrical wiring) but this is a compromise which does not affect the number of available contacts nor the balanced character of the cable.

You always need to make sure that the internal turntable and tonearm wiring is symmetrical (not coaxial) and that at no point the cartridge/tonearm/turntable ground is connected to the signal negative (-ve). All of the cables we prepare for this connection are configured with their shields isolated from the signal -ve for their entire length icluding the connectors.