Technically, it isn't needed per se, you just need to make it so that an actor that should be able to block has the block state on them. There are ways to do that without using passive states, but that is the most simple way to do it.
With the power of hindsight, and two more years of experience, there are definitely things I would do different, and in fact, have done differently with the MZ version of this plugin. Alas, porting those changes to the MV version is probably inadvisable due to the number of changes users would have to make to get it working again.
~Ramza