Lead Sources are counted based on referring URL and any UTM passed. Google and others "group" for example in the User Acquisition Report.
When looking at Web Session Lead Sources, there are a few things to consider.
1. We "count" based on the referring URL and any UTM passed. So whatever is passed, is counted.
2. Due to volume, we also aggregate into the top 5, 10, 15 or 20 so expand that filter to see more.
3. Google Analytics 4 counts based on groupings, with their proprietary definitions like Paid Search, Organic Search, Cross-network and more. In comparing clear categories like google-organic, we come very close to matching.
4. Other can capture a variety, especially if you pass UTM on many campaigns. When your broadcast event creates a search, that the user then clicks on Search Ad, that information will pass through, and be counted.