[Edi]

It is probably the same as "on hit", unless there is some way to determine that it actually uses a different flag. If you look at actual weapon data, Smasher has crusherknack as secondaryeffect, which means it only affects the target on hit. If it were a secondaryeffectalways type of extra effect, then it would hit regardless of whether the smasher blow hit or missed.

I don't know if you have looked at the Dom3 DB, but it has a page with the data on magic items, so you may find some useful information in there. It is substantially expanded from the Dom2 DB, so much so that the two documents have fairly little in common besides the naming conventions.