The logic for this feature actually already exists in the mod, and you have actually already stumbled across it. When having Smart Inserters enabled, QAI takes the back seat and essentially just provides a differnet UI while using Smart Inserter's settings and technologies. But in order for QAI to do that it needed the logic that SI defines with its "Max range of each inserter" setting. So what you are seeing is intended behavior.
Though looking at it it seems like SI has added 3 more options to that setting that QAI currently does not support. Something to fix I suppose.
There is currently no way to access this functionality with just QAI installed. Though I do have a setting for it already and it's basically implemented... but I hid that setting because I was not happy with it. In my notes I have that "Extend only, without gaps" (description: Adjustable range will only extend outwards, however all tiles from the inserter base to the adjustable range will also be reachable. With vanilla and 3 range this causes long handed inserters to be able to reach over beacons and machines which is quite a big difference.) was causing 70 ms spikes with all techs researched when switching to selecting drop with modded inserters which inherently have a long range. I think I was using one from renai transportation for that test (renai is nother beast to add support for that I've not actually dealt with).
So basically I don't like the setting where the inserter just automatically gets reach for all of the inner tiles and then extends outwards. I prefer having a gap there and having it just extend. But then again it's not about what I like anymore, it's about what other people want... so I guess I could just enable that setting and let people use it however they want, even if it's laggy with incredibly long range inserters. "just don't do that"