This is a flawed test because the non-gi version hasn’t been run through lightmass. If you show the SVOGI vs the lightmapped version, the lightmapped version would look better.
You’re showing a 3fps drop in a very isolated case with minimal geometry and no actors. Try showing it in a forest with a lot of trees/actors and get back to be on the fps drop. I’d be willing to bet the drop is in the 10-15fps range.