MSX is a band-aid to cover up low resolution IR. With 80x60 IR, MSX is a useful feature, because without it you often can't tell what you're looking at. But with 320x240 IR it's not needed in most cases. Worse, because the IR and visual lenses aren't coaxial, the resulting parallax error tends to actively deceive you about the exact location of small hot spots.

If FLIR didn't go out of their way to cripple the 320x240 sensors in their low-end models, MSX wouldn't be worth incorporating at all.