Causing block updates at some locations (specifically, near/at spawn) produces large amounts of lag not present at other places in the overworld. The locations that this affects are seemingly random (as far as I've tested), and are much worse in worlds updated from previous versions.

I've attached a video of a short test I've done, as well as the debug report for the world.

Link to video:
https://www.dropbox.com/s/3js37j7nxl6zyln/Minecraft%201.14.4%20Pre-Release%202%20July%205%202_32_59%20P.mp4?dl=0