Yes, it is. They are measuring the milk in isolation, which in this instance means to pour (and measure with your eyes) as it fills the empty container before t

Yes, it is. They are measuring the milk in isolation, which in this instance means to pour (and measure with your eyes) as it fills the empty container before the tea. Whereas you can't really measure how much the volume is changing (eyeballing) in isolation. Think of it as the difference between measuring a liquid in a container and eyeballing a liquid in another liquid.