I have not seen any additional info on the X7 hitch, but hitches in general are not that complicated and the X7 hitch does not seem to be anything very special (and I have experience towing with my Ford Expedition with a weight distribution system installed on my trailer). A weight distributing hitch system consists of additional components that are external to the tow vehicle, some of which are installed on the trailer. Depending on the weight of the tow vehicle and the weight of the trailer, a weight distributing hitch system may not even be necessary if the trailer/tow vehicle combo can stay level when towing.
The air suspension on the X7 serves as a load leveling system when the X7 is towing (not unique to BMW, other truck/SUV manufacturers have been using air suspensions for this purpose for a long time). The air suspension will adjust the rear shocks to help keep the trailer and SUV level, thus acting similar to a weight distribution system. However, the air suspension can only support so much weight, so a weight distribution system may be required to more safely tow heavier loads.
Based on the OPs experience towing his 5000 lb boat, it seems like the air suspension performed well. However, a weight distributing hitch system (with sway control) would only help the X7 tow more weight (up to the max tow limit) even better and with more stability. It will be interesting to see how towing goes for the OP when he tows his heavier load. But I agree with his decision to use a weight distribution system with his heavier trailer.
The link and video below describe how a weight distribution system works.
https://tophitches.com/weight-distribution-hitch-work/