I also found the Omnipod’s way of displaying insulin from an extended bolus in IOB as confusing and annoying. I contacted Insulet support about this and they said they’ll "“make a note of it” - whatever that means… I’m not quite sure that I like the way the Animas Vibe does it either, however. I give a 4u bolus, for example and immediately after delivery, the Vibe might display “3.68U” as IOB - what happened to the other 0.32u? (Note - not a specific precise example.) Knowing things, what happens with an extended bolus becomes more confusing.
Using your example, I scheduled a 4U extended bolus with 2U delivered two and 2 over two hours. The Vibe displayed 1.23U IOB immediately after delivering the 2u, and “BOLUS ACTIVE” to indicate the extended bolus – only via multiple clicks thru the Status menus can the amount of the actual delivery and the balance be discovered. This is a very confusing approach, I think.
I suppose I was spoiled by the Asante Snap, which still did not have it quite right, but did better (It’s been a little while, but I think it did something similar to what Omnipod does, but clearly displayed the actual amount of an extended bolus that was/will be delivered. IOB was immediately corrected if an extended bolus was interrupted - that I remember.)