I didn't receive a list of Rotax or Sensenich supplied parts with my kit either. Further complicating matters for me, the plans were in flux, and I didn't get the revisions for several months after the kit shipped. Some of the Van's supplied bags had parts that weren't needed anymore or listed on the packing list, and some things that where on the packing list were missing. It took a number of emails to Van's and a great deal of patience to sort everything out.
I wish I had better advice, but I think if you make your own list of everything in the engine crate, refer to it when something isn't found elsewhere and contact support if it doesn't make sense, you'll be ok. Things like the exhaust nuts where Van's states are on the engine were buried deep in one of those extra boxes in my kit, for example.
As for the back ordered parts, I ordered my engine in January 2025, it shipped and was delivered in December, but the last back ordered bag just shipped a couple of days ago. I was unfortunate to have run up against two redesigns due to discontinued 3rd party parts, but that was only apparently in retrospect. Van's gave me no information about the delays, which seems to be a common story these days.