Perplexity doesn't actually use Google Search directly. It uses its own indexer and crawler called PerplexityBot [1]. It then uses a mixture of Google and Bing ranking signals to "help" with some of its own search result ranking. I presume they have their own ranker that has some relevancy score based on site recency, cosine similarity of site data with search query, etc, and they combine this with Google and Bing ranking signals.
[1] https://nypost.com/2024/06/28/business/amazon-probing-ai-sta...