trefvelscalar returns the magnitude of velocity (ie: speed) of the bot that's currently tied to it through its active tie. Or that's the idea anyway, it wasn't really ever tested thoroughly I don't think, so there could be odd issues with it.
In this context, it probably should just be considered Muller's ratchet. That is, the breaking of a healthy statement into one that is less useful or useless. I don't see how it could be of all that much use to a bot, even one with a sophisticated tieing system.