I think DuckDuckGo’s developers still try to respect search terms, but since their upstream sources don’t, their results don’t respect search terms.
I doubt Google’s developers are trying to respect search terms. I keep seeing Google highlight results other than the search terms. For example, if I’m searching for “accessibility,” Google and sites using Google, return an absolute scatload of results involving “access,” instead, often password trouble and the like. If I’m searching for “Germanic,” “languages,” etc. I get results involving “German,” instead. If I’m searching for “War of the Rebellion,” in quotes, a collection of documents from the war, “noncombatants,” and some other terms, I get results involving “nullification.” I don’t want to ris adding “-nullification” to exclude this, but that wasn’t one of my search terms and I know it is replacing one of my search terms.