I would imagine it is high-performance within its own domain: soft microprocessors. There isn't much danger of something like this being used outside of domains where it is relevant, so just calling it "high-performance" gets the message across fairly well to anyone who would actually need it.

I can't comment on how well it performs myself without testing it, but a quick skim of the paper reveals that it apparently performs well in comparison to its rival open-source out-of-order soft processor.

Comparing soft processors to other soft processors is fairly easy if they can both run on the same hardware, but comparing them to real silicon is inherently kind of meaningless, as they don't really compete at the moment, and the performance of the design in absolute terms will depend on the FPGA it is implemented on. Nonetheless, you could compare the raw numbers presented in the paper for curiosity's sake and see that indeed, it isn't very fast compared to modern silicon processors.