Multiple blocks such as iron bars, all trapdoors, doors, grass and flowers, and others will disappear (or despawn) prematurely long before their chunks stop being rendered. This has been an issue since before Bedrock Edition existed when the game was called Pocket Edition. The bug has been in Bedrock Edition since day one.  This "feature" was likely implemented to help the game run on devices with 512 MB or less of RAM. We are long past those days, so there is no reason this bug should be present in the game anymore.

This bug is a huge problem for builders, as blocks like iron bars, trapdoors, and doors can be an important part of a structure. Seeing these blocks disappear early while the rest of a structure remains looks ridiculous. I am requesting that this either be completely fixed or add an option for all blocks of every kind to be rendered as long as the chunk is spawned.

In the video, you can see that the iron bars supposed to be holding up this cupola disappear when I get far away, while the rest of the structure remains. It looks ridiculous and should not be happening. This issue does not and did not occur in Java Edition at all.