Counting out all causes of mcpe lag (mobs, light updates, tile entities, villages, etc.) , if removed, what remains is only blocks. And these blocks (although not many) causes game to lag too soon in built up areas. Minecraft Bedrock, compared to Java, lacks in performance in this situation. This bug also addresses the lack of ability to process entities in the nearby vicinity on Bedrock, even when playing with an RTX graphics card from what I've experienced too