FL475 seems unlikely, but equally FL445 10nm south of Penang
The report clearly states that the altitude information from the primary radar does not match the capability of the aircraft (not only the absolute figures, but also the altitude changes), but is known to be very unreliable. It is simply not made for this, radar can detect direction and distance, the closer the plane is to the station the more reliably it can also determine altitude, but not at long ranges.
The report relatively often states, that details are not matching, that events can not be explained... It leaves a lot of room for speculation.
I think they have produced a sound document, there is not much more you can do with the available information.