Would it be possible to add a method into the LimitedRegion to get all TileEntities in a region?
With the old method in BlockPopulator you had access to it via the chunk.
Otherwise you would have to interact over all positions and check if a TileEntity is present, which has a worse performance.

https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/generator/BlockPopulator.html