I don't say so, the file I linked says so and my google searches were fruitless. I had never heard of a Sony having using this Chip.
It's not just the output voltage, which is definitely marginal, it is the lack of current capability, something active preamps with robust regulated supplies deliver unwaveringly. I don't think you have heard this Dac even remotely close to its potential.
Low current capability is not an important parameter if the signal is of low voltage and the impedance of the preamplifier is very high. The main problem of using a passive load is the modulation of the supply voltage to the current sources with the output signal - there is a compromise between amplitude and linearity. I even tried 10 ohms and noise was not a problem, should remember that what is considered the best source, the tape, delivers an output of hundreds of microvolts. But yes, I am sure I have not heard the PCM63 at full capability.
Another myth to add to the unobtainium is the over. Just because it weights the triple or has ten times the power supply energy does not mean it forcefully sounds subjectively better. A few cases where this was found to be true does not create a general rule.