The construction works as a vibe-classifier: name the thing, then name what it evokes. An outfit can be giving "old money," a text can be giving "red flag," a lobby can be giving "dentist office." The comparison can be flattering, neutral, or devastating, which makes it endlessly flexible.
In ballroom-rooted usage, "giving" relates to serving a look — delivering. That is why the standalone "it's giving" (no complement) is praise. The format is firmly mainstream now, used heavily in fashion, interior, and reaction content, and parodied when brands reach for it awkwardly.
