I provided you proof in my next comment. You, otoh, haven't provided any citations.
First, i question your wikipedia source. After going through greek english lexicons. I think it is clear that agnosticism was included in earlier definitions of atheism however it is very clear that atheism is a position.
Here are the uses of the word ἄθεος as found in
A New Greek and English Lexicon
A Greek and English Lexicon published in 1846 by J donnegan
Without god;disbelieving in god, disregarding the gods, wicked, impious; abandoned by or odious to the gods; not knowing the true god and therefore wicked.
Bremmer said:
"The Epicurean Philodemus (ca. 110-35 BC) classified the various kinds of atheists in
antiquity as follows:
(1) Those who say that it is unknown whether there are any gods or what they are like;
(2) Those who say openly that the gods do not exist;
(3) Those who clearly imply it.
-Bremmer, J. N. (2006). Atheism in Antiquity. In M. Martin (Ed.), The Cambridge Companion to Atheism (pp.
11-26). Cambridge: Cambridge University Press.
The term was never intended to be a mere lack of belief as can be said for implicit atheists (such as babies). This is an arbitrary assignment that is not merited by the word construction.
So, we have no reason to accept that atheism meaning merely a "lack of belief" is anything more than arbitrary. I accept that this is how some people have construed the word in modern times. But to say that it is so because that was the logical correlation with the words historic use and construction is not only a poor argument, but an intellectually dishonest one.