I wouldn’t be surprised if GiveWell pursues but doesn’t publish more speculative research of the type you’re mentioning.
I see that they often publish summaries of that kind of research in various places, two random examples:
Malnutrition: https://docs.google.com/spreadsheets/d/15Q3ww3vmZINDsJ2lGNlwdw3amRiiR_y2mkSkbUf1i-g/edit#gid=1814038446 (from https://blog.givewell.org/2021/11/19/malnutrition-treatment/ )
Family planning radio campaigns: https://docs.google.com/document/d/1_k7SBtgCOwMITTyseaz9rzWv3skb7XWts89m8oL6Wb8/edit and https://docs.google.com/spreadsheets/d/1KtjwUbh5za5LKkH2WDe6g8UQ3cOcaRs-dxZgGcvYnDE/edit#gid=18893171 (from their September newsletter)
I see that they often publish summaries of that kind of research in various places, two random examples:
Malnutrition: https://docs.google.com/spreadsheets/d/15Q3ww3vmZINDsJ2lGNlwdw3amRiiR_y2mkSkbUf1i-g/edit#gid=1814038446 (from https://blog.givewell.org/2021/11/19/malnutrition-treatment/ )
Family planning radio campaigns: https://docs.google.com/document/d/1_k7SBtgCOwMITTyseaz9rzWv3skb7XWts89m8oL6Wb8/edit and https://docs.google.com/spreadsheets/d/1KtjwUbh5za5LKkH2WDe6g8UQ3cOcaRs-dxZgGcvYnDE/edit#gid=18893171 (from their September newsletter)