I2S isn’t standardized: it is consistent across the PS Audio products. More detail if you want:
I2S doesn’t have a spec for connector connections, wire impedances, etc. It was only designed for point to point connections on a circuit board (or at most over a short connector in a box.)
I2S does have a spec for what each of the four connections do: bit clock, data, left/right and master clock. The number of bits in each sample aren’t constrained so technically it can be from just a few bits to, say, 64 or whatever bits. The order of the bits is specified that the top bit is the sign, the next bit down is 0.5… so that you can take just as many bits from the beginning of a sample as your device supports (e.g. 16, 24 …) and ignore the rest. The master clock is the one that’s most confusing - in the general case it can be controlled by either end and the word clock, data and l/r don’t have to be aligned with the master clock. The master clock only sets the pace for the rest of the system. Some DACs insist on providing the master clock others take a master clock and still others just ignore it entirely.