Is that your offer (with 2 YoE) or someone else? Is that usual do you think, or do you have some golden stuff on the cv?
I suspect golden stuff on CV / strong interview round. (I'm now a Staff Engineer on 2.5 YoE)
From what I have read Staff Engineer is mostly architecture/meetings/people management, and being across a very large team. If you are doing that it might be Staff Engineer, but if you are mostly coding it probably isn't.
Either way it doesn't matter. It is just another title.