I'm sure it's the same behavior as in 0.10 or 0.11:
Burner inserter <-> Fast belt: Nonono.
Basic inserter <-> Fast Belt: maybe, depends on where you put it. Maybe in curves.
Fast inserter <-> Express belt: Depends - is not reliable, with some "frequencies" of incoming items it cannot grab.
Not a bug. Surprising behavior: yes.
maybe. Maybe also a feature. Not sure about this.
This is normally no problem. If you have a row of 20 furnaces and an express belt, the last inserter (where the item stops/jams) can grab the item without a problem.
So, this behavior is useful to see, if enough items are coming in: If the first furnace in this row doesn't work, then the throughput is still too low. The items are still moving. If they can grab it sometimes, it means: The belt is too long, the items will normally not jam.
The same cannot be told if the inserters can grab per sure: If an furnace at the end gets sometimes an item the overall throughput is eventually still lousy, cause it depends on, in which frequencies the items are coming in. It's an indicator, yes, but it is not reliable with fast/express belts!
A problem comes only, if you built different items on one express belt: The first assembly in that row gets only items, if there is enough throughput, so that the items on the belts are jamming. But there are some ways to make that reliable. It could also be used for the fact, that you built new items (you currently need) at the end and not at the beginning of an belt, so by just placing some fast belts at the right places, you can feed them to the end and the beginning is only feed, if the end doesn't need that much anymore.
From the view of a beginner it is very surprising. But on the other hand it is obvious.
From of view of an advanced player, I would prefer to keep this behavior, because - as said - it is more "reliable" and it is more realistic and if you think a bit also obvious.
If there would not be the fact, that an inserter, that tries to grab something uses also energy, I surely would voter for that, but like so I think it is drawn.