I wouldn't be surprised to find out it is an optional unit like the attack angle sensor for MCAS
However all MAXes did/do have two AoA sensors, and prior to the fixes, regardless of the AoA display option, MCAS only considered one of them.
Even if it leaded to lowering security so much that 4 planes crashed in just a few months.
Only the persistent numeric AoA indicator was optional. And none of this had anything to do with freight, there's no difference in capabilities between the aircraft, it's purely about pilot situational awareness.
https://boeing.mediaroom.com/news-releases-statements?item=1...