Almost always, no — it’s a difference in depth, not a contradiction. Big Y and YFull sequence the Y-chromosome directly and can detect rare, recent mutations that a consumer chip file simply doesn’t cover, so they can name a more recent branch. When they do, that deeper branch is normally a descendant of the one we report — the same lineage, further down.
If you walk up the parent chain of your more-detailed result, you’ll typically arrive back at the branch we placed you on.