Oh, sorry, I should perhaps have specified–this came up when adding vertex colours to loaded geometry that lacked it, as I recall.
For example, in one case I have a rope model, composed of several sections, each being a model loaded from an egg file. For most of my ropes this is fine, but in this one particular case I wanted to additionally have vertex colours shading from the bottom to the top, for use in a shader. So, using GeomVertex -Reader and -Writer, I added them. In 1.9 this didn’t require a call to make_vertex, while in 1.10 it did, I believe.