This issue has arrived along with the new lighting engine and particle files. Whenever there is a block update, the FPS drops significantly. The issue is caused due to a limitation in the CPU. I know Minecraft Java is terribly optimized for running on multiple cores. However it seems even with every setting set to the lowest possible, the lag still exists on a block update. It is the worse with Oak trees when getting into the leaves. Not sure if this can be fixed or not, but this is quite annoying. High Priority doesn't fix the issue either.