I wonder why the linked benchmark site shows g++ to be 27% slower than gcc. Is this just compiling the same C (as subset of C++) program with two different com

I wonder why the linked benchmark site shows g++ to be 27% slower than gcc. Is this just compiling the same C (as subset of C++) program with two different compilers or are they comparing two distinct implementations of the same algorithm ? I didn't see any obvious links to the details of how these benchmarks are run.