Why was the ASA adv 4th out rule changed?

[noobie]

I don't have an ASA rule book earlier than 2005. The '05-'06 rule books both say, in 5-C:

No run shall be scored if a "fourth out" is the result of an appeal of a base missed or left to(o) soon on a runner who has scored.

Does this rule completely exclude all other 4th out possibilities? I don't see the word "only", which prompts me to ask the question. Is this what the Rules Committee really intended?? (which is what I think Dakota was asking originally ... excellent question)

It seems to me that the 4th out has many more possibilities than this, and there's little guidance what to do. But then again, I'm probably overthinking it.