One thing to realize is that the majority of RMC was written around 30 years ago or so. RMC did not change a whole in the reorganization even though some things did change. And that table was one of the things that did not really change.
It is possible that it was put in there for an option that was in another product.
For example, in RMX and in Express Additions #4 there are options (basically the same option) called Rapid Load & Fire, which DOES give a modifier to OB for reloading.