Really. But not exactly like you might assume!
A set or series of functional pottery should be of similar size. This will give the customers confidence in the quality and craftsmanship...and it will stack nicely in cupboards. But aside from these obvious issues, the size of a piece can have a significant effect on the quality of the glaze. Many potters complain about inconsistent glaze effects but can figure out why. Perhaps we should investigate the thickness of the pot wall! A thicker wall picks up more glaze than a thin walled pot. Keep this issue in mind when you make your test tiles...the tiles should simulate the wall thickness of the pot you intend to make.
So, yes, in order to ensure consistent height, diameter and thickness, it is recommended that we weigh and measure our clay. Even if it sounds scientific for no obvious reason!
Here's how I do it. Use a scale to weigh the clay...if you start with the same weight , there is a better likelihood that the finished pieces will have the same dimensions.
Then, I throw the pot to a specified height and diameter using a gauge (and yes, I actually measure it with rulers). This is how I ensure a consistent thickness in the wall of each of the pots in the series.
Consistent wall thickness for each piece in a series will ensure that each piece picks up the same amount of glaze with each dip...and the glaze effects are closer from piece to piece. Of course, there are lots of other factors in the firing of the pot that can effect the glaze, but at least we've ruled out one variable.
So, size (weight, height, diameter, thickness) is important to consistent glazing.