What's likely going on is this. Google is not going to launch an AI computation for every search. That would be lunacy. They're probably identifying some common

What's likely going on is this. Google is not going to launch an AI computation for every search. That would be lunacy. They're probably identifying some commonly occurring searches, running them through AI, and then injecting that AI result whenever those searches occur. They're probably not exact searches but clusters of similar searches. When your search lands into a topic cluster for which there's a pre-computed AI summary, then you get that summary. Distracting adjectives like effing probably spoil the match between your search query and the topic cluster.