Your statements and questions made my head spin.
The device works the same in either ‘direction’. You want the last Ethernet device in your chain to either be on the B side or alone on the A side. If using the B side to feed your last device, you can use other A side ports for various devices and they may realize some benefit from the 12 core transformers but the true value comes from ‘crossing the moat’ from A->B or from B->A (single device).
Hope that helps.
I use fiber to my server so I connect the B side to my upstream distribution switch, and the A SFP port to my server (which in turn connects to my DS via IS2)