First of all, a disclaimer: I am in love with all things Java.
I think you will find, though, that if you have a properly tuned server (and are using a fast JSP engine, like Resin), and your code is properly optimised, then the difference between PHP and JSP is quite small. I will admit , though, that optimising a JSP script is somewhat difficult, because, for example, you have to make sure that you are using the fastest database drivers, and there are several different ways of doing each thing, instead of one. Whereas in PHP, it's mostly just inbuilt functions.
I imagine those tests were done with a "hello, world" script, and they counted the initial compilation time of the JSp into their average. Any self-respecting JSP programmer would have pre-compiled his jsp...
Anyway, JSP isn't that much slower than anyone else, and don't let those benchmarks fool you: it's still the best.