Could be that, but it feels like it weights search-term-proximity higher, and/or tracks more dimensions related to word-connectedness. Like, DDG is more likely to find me a page with all the words but with them scattered about, while Google will get more hits where the words are closer to one another, which is often better specifically for technical searches. Quoting rarely seems to help much, in either case.

[EDIT] Another poster mentioned searches for "X reddit" seeming to have a very-small cap on the number of results from Reddit that it'll display, and that might be part of my problem with SO results, too: maybe their algo prefers to avoid having too many results from one source, which is bad if you expect or want most results to be from one source. That would explain why Google sometimes finds me results with the exact language of my search, that were absent from DDG's listings—maybe it found them, but they got filtered out by a max-from-one-source preference.