That you can go 300km/h in an F1 car, doesn't mean you can go that fast on a bicycle, even though they're both in the genus "wheel-based vehicles for human transport". The jellyfish is a rather different animal. Trees can grow very old, but there's a reason why you didn't use those as an example: too far from human biology. That jellyfish may be at a similar distance.
We have the ability to convert to becoming immortal. It actually happens to some of us. It sucks though. We call this cancer. Turns out the immortal cells become selfish. But you can scrape some off yourself, throw them in a petri dish, supplement growth media, and they will divide forever.
The process of science is to determine what exactly these inferred limits actually are and how many can be overcome.