Yes, setting the PWDNB pin low will reset all registers to their default values, including the serializer and deserializer slave address registers. In the MAX96705, these are registers 0x00 and 0x01, respectively.
For example, say that you change the serializer slave address from 0x80 (default) to 0x82. If PWDNB is set low, the serializer will go back to having 0x80 as its slave address after PWDNB goes high again. The registers are all reset when PWDNB goes low so that PWDNB can be used as a hard reset in a fault condition. When PWDNB goes high, the registers will be in a known state with their default values.