> There’s a certain belief, trust and conviction to lack of a deity in atheism

Atheism means a lack of belief in a god. Just because many atheists go a step further or the word agnostic exists, that doesn't change the meaning.

I have yet to see an "official" source that says it's definitely belief of absence and not absence of belief. Agnosticism works just as well if you view it as subcategory of atheism.