There are multiple distances of jumps based on whether you were walking/running before and how long. While the distance can't be adjusted midair, the direction can.
Not that I like ff14 jumping, but the idea that it's 100% set is just incorrect.
Anyway,
People have asked in various forums for more jump puzzles. It's not laziness to listen to what people ask for, especially for something like moonfire faire which is always a very small event that's supposed to be a giveaway of easy prizes (like emotes).. They ask for it so much that 4.4 will even come with a new MGP event that's going to be a jump puzzle. Tell people, especially in JP, to stop asking for jump puzzles