The term “substantive motion” has been around for a long time and is the term most Australian authorities use. The term “main motion” is used in Robert’s Rules of Order Newly Revised, (RONR) the main authority in the USA.
The term “main motion” makes much more sense to most people as it is obvious what it means. I have therefore switched my terminology from “substantive” to “main”.
I suggest that meetings in Australia and New Zealand and Britain and Canada do the same as the technical term “substantive” is such an unusual word that is causes unnecessary confusion for people who may be having enough trouble just working out the meeting procedure game anyway.
So, use the term “main motion” and you will find a lot less people will be asking what you mean.