This has been the case for a while, but I think the other questions for it have been marked “solved but not really”, and I have a repro project now.
The level streaming system goes back to at least UE3, where I used it a lot. The intended functionality of the “Should Block On Load” parameter of the “Load Stream Level” node is to hitch the main thread until the load is complete when it processes the level streaming next rather than doing it asynchronously.
If Should Block On Load is TRUE, the entire game should freeze up until the entire level is loaded (which will take less time because it’s basically all we’re doing). (pretty sure this is what happens if you press caps lock on the load screen in Xcom 2!)
If Should Block On Load is FALSE, the game continues to play while the level slowly loads in around the player - sometimes, but not always, what you want. And that’s the only result you can get right now with the Level Stream node.
There’s a workaround - call Flush Level Streaming every time you want a blocking load - but that’s not ideal, and currently has problems of its own in some cases:
Here’s a repro project:
http://impromptugames.com/pasta/LevelStreamingFailRepro4032018.7z
This is a show-stopper for multiple projects I’m working on at the moment.