Not by a long shot! Not just for reasons of Adsense revenue, but IMHO also for data to mine re topical relevant websites. HUMINT adds to the relevance of their algorithm(s), said relevance being sorely lacking.
Google's Custom Search Engines (CSE) have been around a long time. I have personally been using it for a few years with no problems. It has helped boost the revenue for several of my sites by improving usability. Search Engine Roundtable ( [seroundtable.com...] ) has also been using it for a long time. If you want to be overly cautious or even paranoid just don't use it.
I had this on my site for 3+ years so it's not new and neither is showing results on your site, surrounded by adsense ads. It's been an option in adsense "adsense for search" for a long time now.
I was aware it's the push that's new, not the search facility itself. I almost used it myself once, but decided it was probably better long-term to create my own search system. Which, incidentally, does not pandalise my sites nor scrape data from them. :)