Yes, when /CS is inactive high, the SDO (data out) pin is high-impedance (tri-stated). The MAX31855 will not drive a signal on the SDO pin when the chip select pin is inactive, and thus will not load the data out signal.
MAX31855
Production
The MAX31855 performs cold-junction compensation and digitizes the signal from a K-, J-, N-, T-, S-, R-, or E-type thermocouple. The data is output in...
Datasheet
MAX31855 on Analog.com