The text on the card says "Express PC and MTP Card" and there is a jumper to select "PC EXP" or "MTP" mode.
Since the MIDI Timepiece has its own S&S MIDI Processor (in addition to the one on the card), the MTP mode must work mostly as a passthru to pass data over the RS422 port. The DB25 port likely becomes inoperative in MTP mode.

However, I don't know if the MPU401 emulation is available in MTP mode.