I'm not aware of any change and that looks normal to me.
If water can go over an edge it goes straight there without spreading.
At least if it's close enough, it can only "see" the edge a certain distance away.
If you want it to spread evenly you can either build the platform so the water just reaches the edge or put a wall around your platform and remove it after the water has spread.
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I tested your setup in 1.14.3 and got the exact same result.
Dear Minecrafters,
Just switched to 1.14.4 and got this issue with water. No mods vanilla version.
In 1.1.4.3 it was OK.
The water spreads around depending on amount of blocks on lower level.
Is it a new feature I have missed or bug?
I'm not aware of any change and that looks normal to me.
If water can go over an edge it goes straight there without spreading.
At least if it's close enough, it can only "see" the edge a certain distance away.
If you want it to spread evenly you can either build the platform so the water just reaches the edge or put a wall around your platform and remove it after the water has spread.
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I tested your setup in 1.14.3 and got the exact same result.
Just testing.