How results are ranked
Results in the live dropdown are ranked by relevance to your query wherever the underlying provider actually supports relevance ranking, which Gmail and GitHub both do.
Where a provider does not expose a relevance signal of its own, results are ranked by recency instead, most recently modified or created first.
In practice this means the most useful match is usually near the top of the dropdown without requiring you to scroll through a long list to find the one you actually meant.
Ranking is applied per query, not learned or personalized over time based on which results you have previously picked; the same query returns results in the same relative order regardless of your past selection history.
If the top result is not the one you meant, refining the query with one more distinguishing word is usually faster than scrolling further down an already-ranked list, since a more specific query tends to reorder the results meaningfully rather than just filtering the same order.