the player would only be built to access DSD 64 either stereo or multichannel in which case the sound would be changed to PCM 176.4 or 88.2.
Nope. It would be a one box CD/SACD player and the AKM 4490 DAC chips used in the BCD3 are entirely capable of running in DSD mode (no conversion to PCM needed), as they are in the BDA3.
Now that someone has mentioned the optical pickup in the BCD3 is also SACD capable that makes the decision even more curious. Audiophile companies like to say "the digital path is optimized for a certain task" but often it is just the path of least resistance. It would be extra effort to implement a dual path properly, it met their design goals as a redbook player and that was it.
The decision can also be ideological. Redbook CD requires no licensing. Other formats require a small licensing fee to be paid to another company for every unit produced. The counter argument is when you add more functionality you broaden the potential customer base and sell more units... hence threads like this are started.