This is a very common Dutch design for bike racks. You use the vertical bar to chain your frame to.
If your groceries are popping your front wheel up, you have a very awkward setup. I’ve only had that happen with very large/weird loads. Normal groceries should be over your rear axle, not behind it.
Not all bikes are the same, but over here 90% of bikes are city bikes, and this rack accommodates that.