It may be more thought out, but it's also almost certainly incorrect. The physical SACD medium requires special hardware support to read resulting in an increase in the cost of the optical pickup mechanism. This is likely the part that was eliminated from the 40GB models since the remainder of the decode / playback process is 100% software. From the relevant Wikipedia entry:
SACD includes various copy protection measures of which the most prominent is Pit Signal Processing (PSP), a physical watermarking feature that contains a digital watermark modulated in the width of pits on the disc (data is stored in the pit length). The optical pickup must contain special circuitry to read the PSP watermark, which is then compared to information on the disc to make sure it's legitimate.