JPGs are defined in-camera via a myriad of settings. Would not trust a camera's JPG as an example of what it can do since there's no real way to know how it was configured. In my experience the only way to know what a camera is capable of is to use it and use it for what one shoots in real life. I take any new camera of my forest photo walks and shoot RAW. JPG is a convenience, but even for "soccer dad" shots I still prefer RAW. I have yet to find an in-camera JPG that pleases me. I must be a tough crowd.
Well, I'm a RAW shooter myself but I know lots of people who shoot mostly JPEG, so JPEG quality IS important.
Anyway, the same comparison page shows that the E-M1 is noticeably WORSE than the E-M5 in RAW, especially at ISO 3200 and up; judging by the low frequency and obnoxious nature of the noise I'd say Olympus decided to follow in the steps of Pentax and employ RAW noise reduction, which is a very bad thing in my book.