My answer assumes it's an older bike with 120mm spacing stock from the factory. Newer, thinner tubes may buckle. For whatever reason, while building a frame the rear spacing tends to shrink, so there is some likelihood that a frame has already been bent. 7mm per side on a robust steel tube is nothing. I recently had this discussion at my favorite bike shop. They were not amused by my position on the topic.
I've seen frames bent more than that, although thank goodness none of mine. If you search the internet for framebuilding pictures, you will probably find some pictures of buckled downtubes.