“God is an ever receding pocket of scientific ignorance that gets smaller and smaller as time goes on” – Neil deGrasse Tyson
“Creationists eagerly seek a gap in present-day knowledge or understanding. If an apparent gap is found, it is assumed that God, by default, must fill it.” – Richard Dawkins
“Ignorance of nature’s ways led people in ancient times to invent gods to lord it over every aspect of human life.” – Stephen Hawking
Yes, people used to marvel at thunder and lightning and come to unreasonable conclusions. They did not know what was going on, and they concluded that God (or gods) must be responsible. This is a gap reasoning.
But when someone is looking at the available evidence and coming to a ‘therefore God exists,” it is not a God of the gaps conclusion. Many of the logical arguments concluding with “therefore, God exists” may be invalid, unsound or totally wrong, but they’re not gap-reasoning.
If someone says, “I don’t know… therefore X,” that is gap-reasoning.
If someone says, “Here are several reasons why it is reasonable to conclude that X,” that is not gap reasoning.