Google Adsense introduced a new search feature to help your search results to be more customized to your site’s themes and topics.
Site-flavored search is an optional feature of AdSense for search that lets you customize your search results to be relevant for your site. Google’s learning technology will flavor your search results to be more customized to your site’s themes and topics.
They say the learning technology used in site-flavored search takes time, so you won’t notice any changes overnight, but gradually your search results should become more relevant to your site.
You need to update your Google Adsense search code to incorporate this feature. I have updated my Google Adsense for Search code, and not much change is seen, but that is expected.