Fluid lag spike in 1.16.1 vanilla

i made a general mob farm designed by gnembon in vanilla single player world in version 1.15.2: https://streamable.com/1pv9tk

and this is what happen in 1.16.1: https://streamable.com/k2cc4n

gamerules:

doMobSpawning: false
doWeatherCycle: false
doDaylightCycle: false

but somehow it have no fluid lag spike in 20w28a, not sure what's going on here and how it gonna affect the future 1.16.2 update: https://streamable.com/saqkdt