Well seeing as the criteria that they used to pick the OpenSSL project is:
"for dramatic improvements to the code quality of OpenSSL"
I think there is a question around why LibreSSL was not chosen seeing as it has done exactly that...
I don't have any numbers but I would guess this would be since OpenSSL is used a lot more than LibreSSL at the moment. So the criteria "and its use in real world systems" would qualify OpenSSL more than LibreSSL.