The article (also reprinted in Best of Dragon, Vol. IV) does two things-
It expands the rules (providing additional weapons that might be used); and
it interprets the rules for edge cases (for example, when you get three attacks in one round, what weapons get used?).
Notably, and this is really the important part .... it takes as the baseline assumption what the actual rule is. In other words, it is additional best evidence as to the extant rule as it existed at the time, especially given that it was published in the TSR house organ.
(Finally, the whole "you only get one additional attack" is something that I only heard of years later- while I am sure there will be people that say they have always played that way, as there always are, I never encountered that until later rule sets that allowed more expansive weapons choices, and it was more of a way to counter the increasing power creep introduced from 1985 on ... more often than not, people tend to read back rules into the text. After all, this is 40 years we are discussing now!).