It may have helped if you read the following text. It provides an example of such a boast (Ezekiel 28:2, “…I am God…” or “…I am a god…”, with the intent of denying God the glory due to him. Therefore, in light of this, other examples are arrogant atheists bragging, “I don’t need God” or “God can’t do anything to me.” These are precise examples of boasting against God’s glory, because they deny what is due to God.
Bragging about keeping someone in the dark hardly constitutes a sin, much less a boast contrary to God’s glory.