My understanding of this is that this is the difference between Passive and Active fail open.
Active fail open is quicker to go into bypass mode than passive and is not available on all of the internal ports, and only on certain sensor models.
I didn't get Passive and Active fail open. I not found any McAfee document describes this.
Sensor (fail-over) always operate as active-active mode.
I agree the documentation is a bit difficult to understand. The best explanation you will find is in the Network Security Platform 8.2 IPS Administration Guide, Chapter 6 (P121) which you can download below or from the links to McAfee Support.
Network Security Platform documentation reference guide
It's still a bit vague on the difference between Active and Passive.
Also the product guide for your sensor will give you some detail on which ports support Active Fail Open.
Network Security Platform NS7x00 Sensor Product Guide
Hope this helps
Some minor details to add on to this - The g3/x ports on a NS-7200 (as well as the other built-in copper ports on other sensor models) have the ability to fail open without an external kit, and act similar to a passive FOK. That's the reason you don't see "In-Line Fail-Open Passive" on that list, which is something you would see on ports with removable interfaces where an external kit is needed. You still have the ability to add an active FOK if you want, which is why that option is available in the menu