Crafting a firework with the fireworks star provided in the creative menu makes a non-exploding firework. The resulting firework is exactly the same as it would be if you left the star out (made a firework out of 1 paper and 1 gunpowder).

Steps to reproduce: get the fireworks star from the creative menu, as well as a handful of paper and gunpowder. Craft a firework out of just 1 paper and 1 gunpowder. Then craft a second firework out of 1 paper, 1 gunpowder and the creative fireworks star. Test both. Neither will explode. Try making a proper basic firework star (1 gunpowder and 1 dye) and making a firework out of it. It will explode as expected.