Bc2000 (for the BCF2000 & BCR2000)

Actually, controller 38 (CC LSB) is optional, and not required by MIDI.  An LSB need only be sent to "fine tune" the MSB.  If the MSB accurately conveys the value, the LSB need not be sent. 

For the logical value of "off" (presumably zero) and a value of "on" (presumably any non-zero) the MSB should be sufficient.  So, I suggest your Prophet is the device at fault here, not the BCR2000.

Apparently the Prophet (incorrectly) insists on receiving both the MSB and LSB for a value of zero (both of which would simply be all zero bits) -- in order to recognize "off" -- when it should be happy with just the MSB.

Btw, I would not surprised if a few rare positions of the rotary dial also transmit only the MSB (that is, when the LSB bits for the value are all zero and thus would add no information if transmitted).

- Matt