bed turns flowing water into block.watersource

It looks like you are using Java Edition or an addon to show entity collision boxes and FPS.

• Bugs in Java Edition should be reported in the Java (MC) project.

• Bugs should be reproducible in vanilla Minecraft.

Those points aside, your video does not show what you describe. It shows you placing a water source and then placing a bed in the water source, and then breaking the bed leaving behind the same water source that you placed beforehand.