What I expected to happen was:

AreaEffectClouds immediately spawn with the correct radius, as they did with versions before 1.9.

What actually happened was:
Until a SetTimePacket is received, the client renders the cloud with the smallest possible radius. Once the time changes, the cloud jumps to the correct calculated radius.

Extra information:

The 1.9 client was updated to make Area Effect Clouds less relying on the server, and added several new data items to make the client simulate radius changing behavior that the server used to be responsible for. Whilst this part works as intended, this change introduced the bug described above.

 
Steps to Reproduce:

• Create a world with the DayCycle turned off
• Throw some lingering potions on the ground
• Notice how they disappear
• Turn on the daycycle gamerule
• Notice how they immediately spawn in correctly

In versions 1.8 and below, lingering potions were not tied to the day cycle.