1) Different STBs / software etc. using different terminology to refer to the same thing - i.e. Toneburst / DisEqC commands.
Correct.
MP uses "simple A" and "simple B" to refer to tone/data burst (also known as unmodulated/modulated). This is a simplified form of DiSEqC for 2 port switches.
Regular DiSEqC is supported: 1.0 (4 port "committed" switches) and 1.2 (positioners). There is no DiSEqC 1.1 (16 port "uncommitted" switch) support in MP at present.
For DiSEqC 1.0 in MP:
AA = port 1 or port A
AB = port 2 or port B
BA = port 3 or port C
BB = port 4 or port D
DiSEqC 1.2 is for positioners, so irrelevant to this discussion.
2) Different switches respond to different commands, and often respond to multiple commands.
This is true.
For example I used a switch that would respond to Toneburst A / B or DisEqC AA / AB to switch between ports (like yours). You could also send DisEqC 1-8 to select any individual LNB input without using 14/18v or 22kHz (just to complicate matters!).
Indeed. Mine only seems to work with AA + AB/BB - uncommitted commands (which aren't supported anyway) don't seem to work.