A fair question, so allow me to elucidate.
Splicing jellyfish into plants without conducting extended studies in restricted environments is a Bad Thing.
Monsanto/Syngenta wants it in the fields far too fast, and they've been found altering or suppressing research and/or evidence that is not in favor of their products. I can totally understand why? Such development costs hundreds of millions of dollars, and the only way to recoup those costs and make a profit is to get it in the field as fast as possible.
However, as we're already seeing with Round-Up resistant weeds, nature is all too ready and willing to exploit any loophole it can find. And the fossil record has numerous species that found themselves facing a loophole along the span of a few thousand years. Neanderthal is an excellent example? Their nasal passages were designed to conserve heat and moisture in an arctic environment. When the earth started warming up, they started dying of sinus infections, making room for us.
Nature has enough loopholes on it's own, and puts centuries, if not millenia, into developing them. We really can't afford to give it anything new without putting a comparable amount of time and resources into the project to make sure it's safe, and won't come back to haunt us.