That active/passive distinction is only relevant for older technology.
Active matrix LCD vs Passive matrix LCD.
I don't think you can find a passive display for sale anymore. It would be like finding a steam engine to power your car. We just use gasoline or diesel for cars today, not steam engines powered cars. Similarly, we don't use passive matrix monitors now, there just isn't a reason because better technology is already commonplace (unlike a decade or so ago).
Because no computer displays for sale to consumers use passive matrix anymore, there is no longer any reason to specifically mention whether a display is passive matrix or active matrix, because everyone assumes a display will not be passive matrix.
See:
http://www.howstuffworks.com/lcd4.htm